diff --git a/integration/batching-with-context-esModuleInterop/batching.ts b/integration/batching-with-context-esModuleInterop/batching.ts
index 8264b4efc..eb760ceb5 100644
--- a/integration/batching-with-context-esModuleInterop/batching.ts
+++ b/integration/batching-with-context-esModuleInterop/batching.ts
@@ -705,7 +705,7 @@ export class EntityServiceClientImpl<Context extends DataLoaders> implements Ent
       return new DataLoader<string, Entity>((ids) => {
         const request = { ids };
         return this.BatchMapQuery(ctx, request).then((res) => {
-          return ids.map((key) => unwrap(res.entities[key]));
+          return ids.map((key) => res.entities[key] ?? fail());
         });
       }, { cacheKeyFn: hash, ...ctx.rpcDataLoaderOptions });
     });
@@ -771,9 +771,6 @@ function isSet(value: any): boolean {
   return value !== null && value !== undefined;
 }
 
-function unwrap<T>(value: T | undefined | null): T {
-  if (value === undefined || value === null) {
-    throw new Error("Expected value to be defined");
-  }
-  return value;
+function fail(message?: string): never {
+  throw new Error(message ?? "Failed");
 }
diff --git a/integration/batching-with-context/batching.ts b/integration/batching-with-context/batching.ts
index d8d1d29b8..319eee661 100644
--- a/integration/batching-with-context/batching.ts
+++ b/integration/batching-with-context/batching.ts
@@ -705,7 +705,7 @@ export class EntityServiceClientImpl<Context extends DataLoaders> implements Ent
       return new DataLoader<string, Entity>((ids) => {
         const request = { ids };
         return this.BatchMapQuery(ctx, request).then((res) => {
-          return ids.map((key) => unwrap(res.entities[key]));
+          return ids.map((key) => res.entities[key] ?? fail());
         });
       }, { cacheKeyFn: hash, ...ctx.rpcDataLoaderOptions });
     });
@@ -771,9 +771,6 @@ function isSet(value: any): boolean {
   return value !== null && value !== undefined;
 }
 
-function unwrap<T>(value: T | undefined | null): T {
-  if (value === undefined || value === null) {
-    throw new Error("Expected value to be defined");
-  }
-  return value;
+function fail(message?: string): never {
+  throw new Error(message ?? "Failed");
 }
diff --git a/integration/extensions/test.ts b/integration/extensions/test.ts
index 20583ea21..03cf234d9 100644
--- a/integration/extensions/test.ts
+++ b/integration/extensions/test.ts
@@ -485,7 +485,7 @@ export const bytes: Extension<Uint8Array> = {
     return encoded;
   },
   decode: (tag: number, input: Uint8Array[]): Uint8Array => {
-    const reader = _m0.Reader.create(unwrap(input[input.length - 1]));
+    const reader = _m0.Reader.create(input[input.length - 1] ?? fail());
     return reader.bytes();
   },
 };
@@ -505,7 +505,7 @@ export const string: Extension<string> = {
     return encoded;
   },
   decode: (tag: number, input: Uint8Array[]): string => {
-    const reader = _m0.Reader.create(unwrap(input[input.length - 1]));
+    const reader = _m0.Reader.create(input[input.length - 1] ?? fail());
     return reader.string();
   },
 };
@@ -525,7 +525,7 @@ export const long: Extension<Long> = {
     return encoded;
   },
   decode: (tag: number, input: Uint8Array[]): Long => {
-    const reader = _m0.Reader.create(unwrap(input[input.length - 1]));
+    const reader = _m0.Reader.create(input[input.length - 1] ?? fail());
     return reader.int64() as Long;
   },
 };
@@ -545,7 +545,7 @@ export const fixed: Extension<Long> = {
     return encoded;
   },
   decode: (tag: number, input: Uint8Array[]): Long => {
-    const reader = _m0.Reader.create(unwrap(input[input.length - 1]));
+    const reader = _m0.Reader.create(input[input.length - 1] ?? fail());
     return reader.fixed64() as Long;
   },
 };
@@ -565,7 +565,7 @@ export const enumField: Extension<Enum> = {
     return encoded;
   },
   decode: (tag: number, input: Uint8Array[]): Enum => {
-    const reader = _m0.Reader.create(unwrap(input[input.length - 1]));
+    const reader = _m0.Reader.create(input[input.length - 1] ?? fail());
     return reader.int32() as any;
   },
 };
@@ -583,7 +583,7 @@ export const group: Extension<Group> = {
     return encoded;
   },
   decode: (tag: number, input: Uint8Array[]): Group => {
-    const reader = _m0.Reader.create(unwrap(input[input.length - 1]));
+    const reader = _m0.Reader.create(input[input.length - 1] ?? fail());
     return Group.decode(reader);
   },
 };
@@ -621,9 +621,6 @@ export interface Extension<T> {
   packed: boolean;
 }
 
-function unwrap<T>(value: T | undefined | null): T {
-  if (value === undefined || value === null) {
-    throw new Error("Expected value to be defined");
-  }
-  return value;
+function fail(message?: string): never {
+  throw new Error(message ?? "Failed");
 }
diff --git a/src/generate-services.ts b/src/generate-services.ts
index aa9061fcb..2fe599fcf 100644
--- a/src/generate-services.ts
+++ b/src/generate-services.ts
@@ -259,7 +259,7 @@ function generateBatchingRpcMethod(ctx: Context, batchMethod: BatchMethod): Code
     // If the return type is a map, lookup each key in the result
     lambda.push(code`
       return this.${methodDesc.formattedName}(ctx, request).then(res => {
-        return ${inputFieldName}.map(key => ${ctx.utils.unwrap}(res.${outputFieldName}[key]))
+        return ${inputFieldName}.map(key => res.${outputFieldName}[key] ?? ${ctx.utils.fail}())
       });
     `);
   } else {
diff --git a/src/main.ts b/src/main.ts
index f46c5d3b4..a4860b127 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -837,19 +837,16 @@ function makeExtensionClass(options: Options) {
 }
 
 function makeAssertionUtils() {
-  const unwrap = conditionalOutput(
-    "unwrap",
+  const fail = conditionalOutput(
+    "fail",
     code`
-    function unwrap<T>(value: T | undefined | null): T {
-      if (value === undefined || value === null) {
-        throw new Error('Expected value to be defined');
+      function fail(message?: string): never {
+        throw new Error(message ?? "Failed");
       }
-      return value;
-    }
     `
   );
 
-  return { unwrap };
+  return { fail };
 }
 
 // Create the interface with properties
@@ -1689,7 +1686,7 @@ function generateExtension(ctx: Context, message: DescriptorProto | undefined, e
     } else {
       // pick the last entry, since it overrides all previous entries if not repeated
       chunks.push(code`
-          const reader = ${Reader}.create(${ctx.utils.unwrap}(input[input.length -1]));
+          const reader = ${Reader}.create(input[input.length -1] ?? ${ctx.utils.fail}());
           return ${readSnippet};
         },
       `);