diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 5edd93599e5..548cf171ca7 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -2448,6 +2448,11 @@
 //	GOARM
 //		For GOARCH=arm, the ARM architecture for which to compile.
 //		Valid values are 5, 6, 7.
+//		When the Go tools are built on an arm system,
+//		the default value is set based on what the build system supports.
+//		When the Go tools are not built on an arm system
+//		(that is, when building a cross-compiler),
+//		the default value is 7.
 //		The value can be followed by an option specifying how to implement floating point instructions.
 //		Valid options are ,softfloat (default for 5) and ,hardfloat (default for 6 and 7).
 //	GOARM64
diff --git a/src/cmd/go/internal/help/helpdoc.go b/src/cmd/go/internal/help/helpdoc.go
index 3db3ed06b2c..3e7a1cbc75d 100644
--- a/src/cmd/go/internal/help/helpdoc.go
+++ b/src/cmd/go/internal/help/helpdoc.go
@@ -620,6 +620,11 @@ Architecture-specific environment variables:
 	GOARM
 		For GOARCH=arm, the ARM architecture for which to compile.
 		Valid values are 5, 6, 7.
+		When the Go tools are built on an arm system,
+		the default value is set based on what the build system supports.
+		When the Go tools are not built on an arm system
+		(that is, when building a cross-compiler),
+		the default value is 7.
 		The value can be followed by an option specifying how to implement floating point instructions.
 		Valid options are ,softfloat (default for 5) and ,hardfloat (default for 6 and 7).
 	GOARM64