diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 5db4bc6bec..c81bd40864 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -93,7 +93,8 @@ and test commands:
 		Supported only on linux/amd64, freebsd/amd64, darwin/amd64 and windows/amd64.
 	-msan
 		enable interoperation with memory sanitizer.
-		Supported only on linux/amd64.
+		Supported only on linux/amd64,
+		and only with Clang/LLVM as the host C compiler.
 	-v
 		print the names of packages as they are compiled.
 	-work
diff --git a/src/cmd/go/build.go b/src/cmd/go/build.go
index 12867004aa..a1f925ed0b 100644
--- a/src/cmd/go/build.go
+++ b/src/cmd/go/build.go
@@ -72,7 +72,8 @@ and test commands:
 		Supported only on linux/amd64, freebsd/amd64, darwin/amd64 and windows/amd64.
 	-msan
 		enable interoperation with memory sanitizer.
-		Supported only on linux/amd64.
+		Supported only on linux/amd64,
+		and only with Clang/LLVM as the host C compiler.
 	-v
 		print the names of packages as they are compiled.
 	-work