diff --git a/src/cargo/core/compiler/build_config.rs b/src/cargo/core/compiler/build_config.rs
index 1add81d0e58..2de8fb575d9 100644
--- a/src/cargo/core/compiler/build_config.rs
+++ b/src/cargo/core/compiler/build_config.rs
@@ -1,6 +1,8 @@
 use std::path::Path;
 use std::cell::RefCell;
 
+use serde::ser;
+
 use util::{CargoResult, CargoResultExt, Config, RustfixDiagnosticServer};
 
 /// Configuration information for a rustc build.
@@ -136,6 +138,24 @@ pub enum CompileMode {
     RunCustomBuild,
 }
 
+impl ser::Serialize for CompileMode {
+    fn serialize<S>(&self, s: S) -> Result<S::Ok, S::Error>
+    where
+        S: ser::Serializer,
+    {
+        use self::CompileMode::*;
+        match *self {
+            Test => "test".serialize(s),
+            Build => "build".serialize(s),
+            Check { .. } => "check".serialize(s),
+            Bench => "bench".serialize(s),
+            Doc { .. } => "doc".serialize(s),
+            Doctest => "doctest".serialize(s),
+            RunCustomBuild => "run-custom-build".serialize(s),
+        }
+    }
+}
+
 impl CompileMode {
     /// Returns true if the unit is being checked.
     pub fn is_check(self) -> bool {
diff --git a/src/cargo/core/compiler/build_plan.rs b/src/cargo/core/compiler/build_plan.rs
index 5813e29906b..28625c7de9e 100644
--- a/src/cargo/core/compiler/build_plan.rs
+++ b/src/cargo/core/compiler/build_plan.rs
@@ -9,7 +9,7 @@
 use std::collections::BTreeMap;
 
 use core::TargetKind;
-use super::{Context, Kind, Unit};
+use super::{CompileMode, Context, Kind, Unit};
 use super::context::OutputFile;
 use util::{internal, CargoResult, ProcessBuilder};
 use std::path::PathBuf;
@@ -22,6 +22,7 @@ struct Invocation {
     package_version: semver::Version,
     target_kind: TargetKind,
     kind: Kind,
+    compile_mode: CompileMode,
     deps: Vec<usize>,
     outputs: Vec<PathBuf>,
     links: BTreeMap<PathBuf, PathBuf>,
@@ -51,6 +52,7 @@ impl Invocation {
             package_version: id.version().clone(),
             kind: unit.kind,
             target_kind: unit.target.kind().clone(),
+            compile_mode: unit.mode,
             deps,
             outputs: Vec::new(),
             links: BTreeMap::new(),
diff --git a/tests/testsuite/build_plan.rs b/tests/testsuite/build_plan.rs
index fa17a79067d..7b520cfd699 100644
--- a/tests/testsuite/build_plan.rs
+++ b/tests/testsuite/build_plan.rs
@@ -28,7 +28,8 @@ fn cargo_build_plan_simple() {
                 "package_name": "foo",
                 "package_version": "0.5.0",
                 "program": "rustc",
-                "target_kind": ["bin"]
+                "target_kind": ["bin"],
+                "compile_mode": "build"
             }
         ]
     }
@@ -86,7 +87,8 @@ fn cargo_build_plan_single_dep() {
                 "package_name": "bar",
                 "package_version": "0.0.1",
                 "program": "rustc",
-                "target_kind": ["lib"]
+                "target_kind": ["lib"],
+                "compile_mode": "build"
             },
             {
                 "args": "{...}",
@@ -101,7 +103,8 @@ fn cargo_build_plan_single_dep() {
                 "package_name": "foo",
                 "package_version": "0.5.0",
                 "program": "rustc",
-                "target_kind": ["lib"]
+                "target_kind": ["lib"],
+                "compile_mode": "build"
             }
         ]
     }
@@ -148,7 +151,8 @@ fn cargo_build_plan_build_script() {
                 "package_name": "foo",
                 "package_version": "0.5.0",
                 "program": "rustc",
-                "target_kind": ["custom-build"]
+                "target_kind": ["custom-build"],
+                "compile_mode": "build"
             },
             {
                 "args": "{...}",
@@ -161,7 +165,8 @@ fn cargo_build_plan_build_script() {
                 "package_name": "foo",
                 "package_version": "0.5.0",
                 "program": "[..]/build-script-build",
-                "target_kind": ["custom-build"]
+                "target_kind": ["custom-build"],
+                "compile_mode": "run-custom-build"
             },
             {
                 "args": "{...}",
@@ -174,7 +179,8 @@ fn cargo_build_plan_build_script() {
                 "package_name": "foo",
                 "package_version": "0.5.0",
                 "program": "rustc",
-                "target_kind": ["bin"]
+                "target_kind": ["bin"],
+                "compile_mode": "build"
             }
         ]
     }
diff --git a/tests/testsuite/metabuild.rs b/tests/testsuite/metabuild.rs
index c96f0c4b6b6..7837042b1d1 100644
--- a/tests/testsuite/metabuild.rs
+++ b/tests/testsuite/metabuild.rs
@@ -433,6 +433,7 @@ fn metabuild_build_plan() {
             "package_name": "mb",
             "package_version": "0.5.0",
             "target_kind": ["lib"],
+            "compile_mode": "build",
             "kind": "Host",
             "deps": [],
             "outputs": ["[..]/target/debug/deps/libmb-[..].rlib"],
@@ -446,6 +447,7 @@ fn metabuild_build_plan() {
             "package_name": "mb-other",
             "package_version": "0.0.1",
             "target_kind": ["lib"],
+            "compile_mode": "build",
             "kind": "Host",
             "deps": [],
             "outputs": ["[..]/target/debug/deps/libmb_other-[..].rlib"],
@@ -459,6 +461,7 @@ fn metabuild_build_plan() {
             "package_name": "foo",
             "package_version": "0.0.1",
             "target_kind": ["custom-build"],
+            "compile_mode": "build",
             "kind": "Host",
             "deps": [0, 1],
             "outputs": ["[..]/target/debug/build/foo-[..]/metabuild_foo-[..][EXE]"],
@@ -472,6 +475,7 @@ fn metabuild_build_plan() {
             "package_name": "foo",
             "package_version": "0.0.1",
             "target_kind": ["custom-build"],
+            "compile_mode": "run-custom-build",
             "kind": "Host",
             "deps": [2],
             "outputs": [],
@@ -485,6 +489,7 @@ fn metabuild_build_plan() {
             "package_name": "foo",
             "package_version": "0.0.1",
             "target_kind": ["lib"],
+            "compile_mode": "build",
             "kind": "Host",
             "deps": [3],
             "outputs": ["[..]/foo/target/debug/deps/libfoo-[..].rlib"],