diff --git a/android/soongconfig/config.go b/android/soongconfig/config.go
index 39a776c..c72da2f 100644
--- a/android/soongconfig/config.go
+++ b/android/soongconfig/config.go
@@ -14,7 +14,10 @@
 
 package soongconfig
 
-import "strings"
+import (
+	"fmt"
+	"strings"
+)
 
 type SoongConfig interface {
 	// Bool interprets the variable named `name` as a boolean, returning true if, after
@@ -31,7 +34,16 @@
 }
 
 func Config(vars map[string]string) SoongConfig {
-	return soongConfig(vars)
+	configVars := make(map[string]string)
+	if len(vars) > 0 {
+		for k, v := range vars {
+			configVars[k] = v
+		}
+		if _, exists := configVars[conditionsDefault]; exists {
+			panic(fmt.Sprintf("%q is a reserved soong config variable name", conditionsDefault))
+		}
+	}
+	return soongConfig(configVars)
 }
 
 type soongConfig map[string]string