diff --git a/java/builder.go b/java/builder.go
index b5dc88a..417a7fa 100644
--- a/java/builder.go
+++ b/java/builder.go
@@ -313,7 +313,7 @@
 			// ensure turbine does not fall back to the default bootclasspath.
 			bootClasspath = `--bootclasspath ""`
 		} else {
-			bootClasspath = strings.Join(flags.bootClasspath.FormTurbineClasspath("--bootclasspath "), " ")
+			bootClasspath = flags.bootClasspath.FormTurbineClassPath("--bootclasspath ")
 		}
 	}
 
@@ -330,7 +330,7 @@
 			"javacFlags":    flags.javacFlags,
 			"bootClasspath": bootClasspath,
 			"srcJars":       strings.Join(srcJars.Strings(), " "),
-			"classpath":     strings.Join(classpath.FormTurbineClasspath("--classpath "), " "),
+			"classpath":     classpath.FormTurbineClassPath("--classpath "),
 			"outDir":        android.PathForModuleOut(ctx, "turbine", "classes").String(),
 			"javaVersion":   flags.javaVersion.String(),
 		},
@@ -523,18 +523,26 @@
 
 type classpath android.Paths
 
-func (x *classpath) FormJavaClassPath(optName string) string {
+func (x *classpath) formJoinedClassPath(optName string, sep string) string {
 	if optName != "" && !strings.HasSuffix(optName, "=") && !strings.HasSuffix(optName, " ") {
 		optName += " "
 	}
 	if len(*x) > 0 {
-		return optName + strings.Join(x.Strings(), ":")
+		return optName + strings.Join(x.Strings(), sep)
 	} else {
 		return ""
 	}
 }
+func (x *classpath) FormJavaClassPath(optName string) string {
+	return x.formJoinedClassPath(optName, ":")
+}
 
-func (x *classpath) FormTurbineClasspath(optName string) []string {
+func (x *classpath) FormTurbineClassPath(optName string) string {
+	return x.formJoinedClassPath(optName, " ")
+}
+
+// FormRepeatedClassPath returns a list of arguments with the given optName prefixed to each element of the classpath.
+func (x *classpath) FormRepeatedClassPath(optName string) []string {
 	if x == nil || *x == nil {
 		return nil
 	}
diff --git a/java/dex.go b/java/dex.go
index c8a4fa8..5b25b21 100644
--- a/java/dex.go
+++ b/java/dex.go
@@ -85,8 +85,8 @@
 func (j *Module) d8Flags(ctx android.ModuleContext, flags javaBuilderFlags) ([]string, android.Paths) {
 	d8Flags := j.dexCommonFlags(ctx)
 
-	d8Flags = append(d8Flags, flags.bootClasspath.FormTurbineClasspath("--lib ")...)
-	d8Flags = append(d8Flags, flags.classpath.FormTurbineClasspath("--lib ")...)
+	d8Flags = append(d8Flags, flags.bootClasspath.FormRepeatedClassPath("--lib ")...)
+	d8Flags = append(d8Flags, flags.classpath.FormRepeatedClassPath("--lib ")...)
 
 	var d8Deps android.Paths
 	d8Deps = append(d8Deps, flags.bootClasspath...)
diff --git a/java/kotlin.go b/java/kotlin.go
index aa65314..5319a4f 100644
--- a/java/kotlin.go
+++ b/java/kotlin.go
@@ -133,7 +133,7 @@
 	deps = append(deps, srcJars...)
 	deps = append(deps, flags.processorPath...)
 
-	kaptProcessorPath := flags.processorPath.FormTurbineClasspath("-P plugin:org.jetbrains.kotlin.kapt3:apclasspath=")
+	kaptProcessorPath := flags.processorPath.FormRepeatedClassPath("-P plugin:org.jetbrains.kotlin.kapt3:apclasspath=")
 
 	kaptProcessor := ""
 	if flags.processor != "" {