diff --git a/src/cmd/compile/internal/base/flag.go b/src/cmd/compile/internal/base/flag.go
index 7bd27c92a3d..6d9497c3a93 100644
--- a/src/cmd/compile/internal/base/flag.go
+++ b/src/cmd/compile/internal/base/flag.go
@@ -98,6 +98,7 @@ type CmdFlags struct {
 	DwarfLocationLists *bool        "help:\"add location lists to DWARF in optimized mode\""                      // &Ctxt.Flag_locationlists, set below
 	Dynlink            *bool        "help:\"support references to Go symbols defined in other shared libraries\"" // &Ctxt.Flag_dynlink, set below
 	EmbedCfg           func(string) "help:\"read go:embed configuration from `file`\""
+	Env                func(string) "help:\"add `definition` of the form key=value to environment\""
 	GenDwarfInl        int          "help:\"generate DWARF inline info records\"" // 0=disabled, 1=funcs, 2=funcs+formals/locals
 	GoVersion          string       "help:\"required version of the runtime\""
 	ImportCfg          func(string) "help:\"read import configuration from `file`\""
@@ -143,6 +144,14 @@ type CmdFlags struct {
 	}
 }
 
+func addEnv(s string) {
+	i := strings.Index(s, "=")
+	if i < 0 {
+		log.Fatal("-env argument must be of the form key=value")
+	}
+	os.Setenv(s[:i], s[i+1:])
+}
+
 // ParseFlags parses the command-line flags into Flag.
 func ParseFlags() {
 	Flag.I = addImportDir
@@ -158,6 +167,7 @@ func ParseFlags() {
 	*Flag.DwarfLocationLists = true
 	Flag.Dynlink = &Ctxt.Flag_dynlink
 	Flag.EmbedCfg = readEmbedCfg
+	Flag.Env = addEnv
 	Flag.GenDwarfInl = 2
 	Flag.ImportCfg = readImportCfg
 	Flag.CoverageCfg = readCoverageCfg