diff --git a/google/internal/externalaccount/header.go b/google/internal/externalaccount/header.go
index 64bec92..1d5aad2 100644
--- a/google/internal/externalaccount/header.go
+++ b/google/internal/externalaccount/header.go
@@ -32,6 +32,8 @@ func goVersion() string {
 			s = s[:p]
 		}
 		return s
+	} else if p := strings.IndexFunc(s, unicode.IsSpace); p >= 0 {
+		s = s[:p]
 	}
 
 	notSemverRune := func(r rune) bool {
diff --git a/google/internal/externalaccount/header_test.go b/google/internal/externalaccount/header_test.go
index e9ce4b6..39f279d 100644
--- a/google/internal/externalaccount/header_test.go
+++ b/google/internal/externalaccount/header_test.go
@@ -5,6 +5,7 @@
 package externalaccount
 
 import (
+	"runtime"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -43,4 +44,5 @@ func TestGoVersion(t *testing.T) {
 			t.Errorf("got(-),want(+):\n%s", diff)
 		}
 	}
+	version = runtime.Version
 }