diff --git a/features/wasm/wasm.go b/features/wasm/wasm.go
index 009768ed28..8e8e52ea2d 100644
--- a/features/wasm/wasm.go
+++ b/features/wasm/wasm.go
@@ -64,6 +64,7 @@ func (o *OPA) Eval(ctx context.Context, opts opa.EvalOpts) (*opa.Result, error)
 		Time:                   opts.Time,
 		Seed:                   opts.Seed,
 		InterQueryBuiltinCache: opts.InterQueryBuiltinCache,
+		PrintHook:              opts.PrintHook,
 	}
 
 	res, err := o.opa.Eval(ctx, evalOptions)
diff --git a/internal/compiler/wasm/wasm.go b/internal/compiler/wasm/wasm.go
index 2e5c064c55..e415f5f3fd 100644
--- a/internal/compiler/wasm/wasm.go
+++ b/internal/compiler/wasm/wasm.go
@@ -21,6 +21,7 @@ import (
 	"github.com/open-policy-agent/opa/internal/wasm/instruction"
 	"github.com/open-policy-agent/opa/internal/wasm/module"
 	"github.com/open-policy-agent/opa/internal/wasm/types"
+	opatypes "github.com/open-policy-agent/opa/types"
 )
 
 // Record Wasm ABI version in exported global variable
@@ -179,6 +180,11 @@ var builtinsUsingRE2 = [...]string{
 	builtinsFunctions[ast.GlobMatch.Name],
 }
 
+type externalFunc struct {
+	ID   int32
+	Decl *opatypes.Function
+}
+
 var builtinDispatchers = [...]string{
 	"opa_builtin0",
 	"opa_builtin1",
@@ -198,17 +204,17 @@ type Compiler struct {
 
 	funcsCode []funcCode // compile functions' code
 
-	builtinStringAddrs    map[int]uint32     // addresses of built-in string constants
-	externalFuncNameAddrs map[string]int32   // addresses of required built-in function names for listing
-	externalFuncs         map[string]int32   // required built-in function ids
-	entrypointNameAddrs   map[string]int32   // addresses of available entrypoint names for listing
-	entrypoints           map[string]int32   // available entrypoint ids
-	stringOffset          int32              // null-terminated string data base offset
-	stringAddrs           []uint32           // null-terminated string constant addresses
-	opaStringAddrs        []uint32           // addresses of interned opa_string_t
-	opaBoolAddrs          map[ir.Bool]uint32 // addresses of interned opa_boolean_t
-	fileAddrs             []uint32           // null-terminated string constant addresses, used for file names
-	funcs                 map[string]uint32  // maps imported and exported function names to function indices
+	builtinStringAddrs    map[int]uint32          // addresses of built-in string constants
+	externalFuncNameAddrs map[string]int32        // addresses of required built-in function names for listing
+	externalFuncs         map[string]externalFunc // required built-in function ids and types
+	entrypointNameAddrs   map[string]int32        // addresses of available entrypoint names for listing
+	entrypoints           map[string]int32        // available entrypoint ids
+	stringOffset          int32                   // null-terminated string data base offset
+	stringAddrs           []uint32                // null-terminated string constant addresses
+	opaStringAddrs        []uint32                // addresses of interned opa_string_t
+	opaBoolAddrs          map[ir.Bool]uint32      // addresses of interned opa_boolean_t
+	fileAddrs             []uint32                // null-terminated string constant addresses, used for file names
+	funcs                 map[string]uint32       // maps imported and exported function names to function indices
 
 	nextLocal uint32
 	locals    map[ir.Local]uint32
@@ -567,7 +573,7 @@ func (c *Compiler) compileExternalFuncDecls() error {
 
 	c.appendInstr(instruction.Call{Index: c.function(opaObject)})
 	c.appendInstr(instruction.SetLocal{Index: lobj})
-	c.externalFuncs = make(map[string]int32)
+	c.externalFuncs = make(map[string]externalFunc)
 
 	for index, decl := range c.policy.Static.BuiltinFuncs {
 		if _, ok := builtinsFunctions[decl.Name]; !ok {
@@ -577,7 +583,7 @@ func (c *Compiler) compileExternalFuncDecls() error {
 			c.appendInstr(instruction.I64Const{Value: int64(index)})
 			c.appendInstr(instruction.Call{Index: c.function(opaNumberInt)})
 			c.appendInstr(instruction.Call{Index: c.function(opaObjectInsert)})
-			c.externalFuncs[decl.Name] = int32(index)
+			c.externalFuncs[decl.Name] = externalFunc{ID: int32(index), Decl: decl.Decl}
 		}
 	}
 
@@ -1428,8 +1434,8 @@ func (c *Compiler) compileCallStmt(stmt *ir.CallStmt, result *[]instruction.Inst
 		return c.compileInternalCall(stmt, index, result)
 	}
 
-	if id, ok := c.externalFuncs[fn]; ok {
-		return c.compileExternalCall(stmt, id, result)
+	if ef, ok := c.externalFuncs[fn]; ok {
+		return c.compileExternalCall(stmt, ef, result)
 	}
 
 	c.errors = append(c.errors, fmt.Errorf("undefined function: %q", fn))
@@ -1457,7 +1463,7 @@ func (c *Compiler) compileInternalCall(stmt *ir.CallStmt, index uint32, result *
 	return nil
 }
 
-func (c *Compiler) compileExternalCall(stmt *ir.CallStmt, id int32, result *[]instruction.Instruction) error {
+func (c *Compiler) compileExternalCall(stmt *ir.CallStmt, ef externalFunc, result *[]instruction.Instruction) error {
 
 	if len(stmt.Args) >= len(builtinDispatchers) {
 		c.errors = append(c.errors, fmt.Errorf("too many built-in call arguments: %q", stmt.Func))
@@ -1465,7 +1471,7 @@ func (c *Compiler) compileExternalCall(stmt *ir.CallStmt, id int32, result *[]in
 	}
 
 	instrs := *result
-	instrs = append(instrs, instruction.I32Const{Value: id})
+	instrs = append(instrs, instruction.I32Const{Value: ef.ID})
 	instrs = append(instrs, instruction.I32Const{Value: 0}) // unused context parameter
 
 	for _, arg := range stmt.Args {
@@ -1473,9 +1479,15 @@ func (c *Compiler) compileExternalCall(stmt *ir.CallStmt, id int32, result *[]in
 	}
 
 	instrs = append(instrs, instruction.Call{Index: c.function(builtinDispatchers[len(stmt.Args)])})
-	instrs = append(instrs, instruction.TeeLocal{Index: c.local(stmt.Result)})
-	instrs = append(instrs, instruction.I32Eqz{})
-	instrs = append(instrs, instruction.BrIf{Index: 0})
+
+	if ef.Decl.Result() != nil {
+		instrs = append(instrs, instruction.TeeLocal{Index: c.local(stmt.Result)})
+		instrs = append(instrs, instruction.I32Eqz{})
+		instrs = append(instrs, instruction.BrIf{Index: 0})
+	} else {
+		instrs = append(instrs, instruction.Drop{})
+	}
+
 	*result = instrs
 	return nil
 }
diff --git a/internal/ir/ir.go b/internal/ir/ir.go
index 6a26af9fb7..decd8f2033 100644
--- a/internal/ir/ir.go
+++ b/internal/ir/ir.go
@@ -10,6 +10,8 @@ package ir
 
 import (
 	"fmt"
+
+	"github.com/open-policy-agent/opa/types"
 )
 
 type (
@@ -31,6 +33,7 @@ type (
 	// policy.
 	BuiltinFunc struct {
 		Name string
+		Decl *types.Function
 	}
 
 	// Plans represents a collection of named query plans to expose in the policy.
diff --git a/internal/planner/planner.go b/internal/planner/planner.go
index 47a54bd063..60810698eb 100644
--- a/internal/planner/planner.go
+++ b/internal/planner/planner.go
@@ -33,7 +33,7 @@ type Planner struct {
 	modules []*ast.Module           // input modules to support queries
 	strings map[string]int          // global string constant indices
 	files   map[string]int          // global file constant indices
-	externs map[string]struct{}     // built-in functions that are required in execution environment
+	externs map[string]*ast.Builtin // built-in functions that are required in execution environment
 	decls   map[string]*ast.Builtin // built-in functions that may be provided in execution environment
 	rules   *ruletrie               // rules that may be planned
 	funcs   *funcstack              // functions that have been planned
@@ -68,7 +68,7 @@ func New() *Planner {
 		},
 		strings: map[string]int{},
 		files:   map[string]int{},
-		externs: map[string]struct{}{},
+		externs: map[string]*ast.Builtin{},
 		lnext:   ir.Unused,
 		vars: newVarstack(map[ast.Var]ir.Local{
 			ast.InputRootDocument.Value.(ast.Var):   ir.Input,
@@ -725,6 +725,7 @@ func (p *Planner) planExprCall(e *ast.Expr, iter planiter) error {
 		var relation bool
 		var name string
 		var arity int
+		var void bool
 		var args []ir.LocalOrConst
 
 		node := p.rules.Lookup(e.Operator())
@@ -743,8 +744,9 @@ func (p *Planner) planExprCall(e *ast.Expr, iter planiter) error {
 		} else if decl, ok := p.decls[operator]; ok {
 			relation = decl.Relation
 			arity = len(decl.Decl.Args())
+			void = decl.Decl.Result() == nil
 			name = operator
-			p.externs[operator] = struct{}{}
+			p.externs[operator] = decl
 		} else {
 			return fmt.Errorf("illegal call: unknown operator %q", operator)
 		}
@@ -759,7 +761,7 @@ func (p *Planner) planExprCall(e *ast.Expr, iter planiter) error {
 			return p.planExprCallRelation(name, arity, operands, args, iter)
 		}
 
-		return p.planExprCallFunc(name, arity, operands, args, iter)
+		return p.planExprCallFunc(name, arity, void, operands, args, iter)
 	}
 }
 
@@ -814,7 +816,7 @@ func (p *Planner) planExprCallRelation(name string, arity int, operands []*ast.T
 	})
 }
 
-func (p *Planner) planExprCallFunc(name string, arity int, operands []*ast.Term, args []ir.LocalOrConst, iter planiter) error {
+func (p *Planner) planExprCallFunc(name string, arity int, void bool, operands []*ast.Term, args []ir.LocalOrConst, iter planiter) error {
 
 	if len(operands) == arity {
 		// definition: f(x) = y { ... }
@@ -828,10 +830,12 @@ func (p *Planner) planExprCallFunc(name string, arity int, operands []*ast.Term,
 				Result: ltarget,
 			})
 
-			p.appendStmt(&ir.NotEqualStmt{
-				A: ltarget,
-				B: ir.Bool(false),
-			})
+			if !void {
+				p.appendStmt(&ir.NotEqualStmt{
+					A: ltarget,
+					B: ir.Bool(false),
+				})
+			}
 
 			return iter()
 		})
@@ -1890,8 +1894,8 @@ func (p *Planner) planExterns() error {
 
 	p.policy.Static.BuiltinFuncs = make([]*ir.BuiltinFunc, 0, len(p.externs))
 
-	for name := range p.externs {
-		p.policy.Static.BuiltinFuncs = append(p.policy.Static.BuiltinFuncs, &ir.BuiltinFunc{Name: name})
+	for name, decl := range p.externs {
+		p.policy.Static.BuiltinFuncs = append(p.policy.Static.BuiltinFuncs, &ir.BuiltinFunc{Name: name, Decl: decl.Decl})
 	}
 
 	sort.Slice(p.policy.Static.BuiltinFuncs, func(i, j int) bool {
diff --git a/internal/rego/opa/options.go b/internal/rego/opa/options.go
index e74a45fec3..ec6b2f0b5a 100644
--- a/internal/rego/opa/options.go
+++ b/internal/rego/opa/options.go
@@ -6,6 +6,7 @@ import (
 
 	"github.com/open-policy-agent/opa/metrics"
 	"github.com/open-policy-agent/opa/topdown/cache"
+	"github.com/open-policy-agent/opa/topdown/print"
 )
 
 // Result holds the evaluation result.
@@ -21,4 +22,5 @@ type EvalOpts struct {
 	Time                   time.Time
 	Seed                   io.Reader
 	InterQueryBuiltinCache cache.InterQueryCache
+	PrintHook              print.Hook
 }
diff --git a/internal/wasm/sdk/internal/wasm/bindings.go b/internal/wasm/sdk/internal/wasm/bindings.go
index 8ed98917a1..6c27e330a4 100644
--- a/internal/wasm/sdk/internal/wasm/bindings.go
+++ b/internal/wasm/sdk/internal/wasm/bindings.go
@@ -23,6 +23,7 @@ import (
 	"github.com/open-policy-agent/opa/topdown"
 	"github.com/open-policy-agent/opa/topdown/builtins"
 	"github.com/open-policy-agent/opa/topdown/cache"
+	"github.com/open-policy-agent/opa/topdown/print"
 )
 
 func opaFunctions(dispatcher *builtinDispatcher, store *wasmtime.Store) map[string]wasmtime.AsExtern {
@@ -80,7 +81,7 @@ func (d *builtinDispatcher) SetMap(m map[int32]topdown.BuiltinFunc) {
 }
 
 // Reset is called in Eval before using the builtinDispatcher.
-func (d *builtinDispatcher) Reset(ctx context.Context, seed io.Reader, ns time.Time, iqbCache cache.InterQueryCache) {
+func (d *builtinDispatcher) Reset(ctx context.Context, seed io.Reader, ns time.Time, iqbCache cache.InterQueryCache, ph print.Hook) {
 	if ns.IsZero() {
 		ns = time.Now()
 	}
@@ -101,6 +102,7 @@ func (d *builtinDispatcher) Reset(ctx context.Context, seed io.Reader, ns time.T
 		QueryID:                0,
 		ParentID:               0,
 		InterQueryBuiltinCache: iqbCache,
+		PrintHook:              ph,
 	}
 
 }
diff --git a/internal/wasm/sdk/internal/wasm/pool_test.go b/internal/wasm/sdk/internal/wasm/pool_test.go
index 39a1783d85..24cb09265d 100644
--- a/internal/wasm/sdk/internal/wasm/pool_test.go
+++ b/internal/wasm/sdk/internal/wasm/pool_test.go
@@ -158,7 +158,7 @@ func ensurePoolResults(t *testing.T, ctx context.Context, testPool *wasm.Pool, p
 		toRelease = append(toRelease, vm)
 
 		cfg, _ := cache.ParseCachingConfig(nil)
-		result, err := vm.Eval(ctx, 0, nil, metrics.New(), rand.New(rand.NewSource(0)), time.Now(), cache.NewInterQueryCache(cfg))
+		result, err := vm.Eval(ctx, 0, nil, metrics.New(), rand.New(rand.NewSource(0)), time.Now(), cache.NewInterQueryCache(cfg), nil)
 		if err != nil {
 			t.Fatalf("Unexpected error: %s", err)
 		}
diff --git a/internal/wasm/sdk/internal/wasm/vm.go b/internal/wasm/sdk/internal/wasm/vm.go
index 0b2ad33c00..ae7ee6cd3a 100644
--- a/internal/wasm/sdk/internal/wasm/vm.go
+++ b/internal/wasm/sdk/internal/wasm/vm.go
@@ -21,6 +21,7 @@ import (
 	"github.com/open-policy-agent/opa/metrics"
 	"github.com/open-policy-agent/opa/topdown"
 	"github.com/open-policy-agent/opa/topdown/cache"
+	"github.com/open-policy-agent/opa/topdown/print"
 )
 
 // VM is a wrapper around a Wasm VM instance
@@ -269,9 +270,10 @@ func (i *VM) Eval(ctx context.Context,
 	metrics metrics.Metrics,
 	seed io.Reader,
 	ns time.Time,
-	iqbCache cache.InterQueryCache) ([]byte, error) {
+	iqbCache cache.InterQueryCache,
+	ph print.Hook) ([]byte, error) {
 	if i.abiMinorVersion < int32(2) {
-		return i.evalCompat(ctx, entrypoint, input, metrics, seed, ns, iqbCache)
+		return i.evalCompat(ctx, entrypoint, input, metrics, seed, ns, iqbCache, ph)
 	}
 
 	metrics.Timer("wasm_vm_eval").Start()
@@ -313,7 +315,7 @@ func (i *VM) Eval(ctx context.Context,
 	// make use of it (e.g. `http.send`); and it will spawn a go routine
 	// cancelling the builtins that use topdown.Cancel, when the context is
 	// cancelled.
-	i.dispatcher.Reset(ctx, seed, ns, iqbCache)
+	i.dispatcher.Reset(ctx, seed, ns, iqbCache, ph)
 
 	metrics.Timer("wasm_vm_eval_call").Start()
 	resultAddr, err := i.evalOneOff(ctx, int32(entrypoint), i.dataAddr, inputAddr, inputLen, heapPtr)
@@ -341,7 +343,8 @@ func (i *VM) evalCompat(ctx context.Context,
 	metrics metrics.Metrics,
 	seed io.Reader,
 	ns time.Time,
-	iqbCache cache.InterQueryCache) ([]byte, error) {
+	iqbCache cache.InterQueryCache,
+	ph print.Hook) ([]byte, error) {
 	metrics.Timer("wasm_vm_eval").Start()
 	defer metrics.Timer("wasm_vm_eval").Stop()
 
@@ -351,7 +354,7 @@ func (i *VM) evalCompat(ctx context.Context,
 	// make use of it (e.g. `http.send`); and it will spawn a go routine
 	// cancelling the builtins that use topdown.Cancel, when the context is
 	// cancelled.
-	i.dispatcher.Reset(ctx, seed, ns, iqbCache)
+	i.dispatcher.Reset(ctx, seed, ns, iqbCache, ph)
 
 	err := i.setHeapState(ctx, i.evalHeapPtr)
 	if err != nil {
diff --git a/internal/wasm/sdk/opa/opa.go b/internal/wasm/sdk/opa/opa.go
index e1a2d97383..95130cc715 100644
--- a/internal/wasm/sdk/opa/opa.go
+++ b/internal/wasm/sdk/opa/opa.go
@@ -17,6 +17,7 @@ import (
 	sdk_errors "github.com/open-policy-agent/opa/internal/wasm/sdk/opa/errors"
 	"github.com/open-policy-agent/opa/metrics"
 	"github.com/open-policy-agent/opa/topdown/cache"
+	"github.com/open-policy-agent/opa/topdown/print"
 )
 
 var errNotReady = errors.New(errors.NotReadyErr, "")
@@ -163,6 +164,7 @@ type EvalOpts struct {
 	Time                   time.Time
 	Seed                   io.Reader
 	InterQueryBuiltinCache cache.InterQueryCache
+	PrintHook              print.Hook
 }
 
 // Eval evaluates the policy with the given input, returning the
@@ -186,7 +188,7 @@ func (o *OPA) Eval(ctx context.Context, opts EvalOpts) (*Result, error) {
 
 	defer o.pool.Release(instance, m)
 
-	result, err := instance.Eval(ctx, opts.Entrypoint, opts.Input, m, opts.Seed, opts.Time, opts.InterQueryBuiltinCache)
+	result, err := instance.Eval(ctx, opts.Entrypoint, opts.Input, m, opts.Seed, opts.Time, opts.InterQueryBuiltinCache, opts.PrintHook)
 	if err != nil {
 		return nil, err
 	}
diff --git a/rego/rego.go b/rego/rego.go
index 1e5ac8641f..a676fc73d7 100644
--- a/rego/rego.go
+++ b/rego/rego.go
@@ -1920,6 +1920,7 @@ func (r *Rego) evalWasm(ctx context.Context, ectx *EvalContext) (ResultSet, erro
 		Time:                   ectx.time,
 		Seed:                   ectx.seed,
 		InterQueryBuiltinCache: ectx.interQueryBuiltinCache,
+		PrintHook:              ectx.printHook,
 	})
 	if err != nil {
 		return nil, err