diff --git a/bp2build/symlink_forest.go b/bp2build/symlink_forest.go
index db7bef8..15a6335 100644
--- a/bp2build/symlink_forest.go
+++ b/bp2build/symlink_forest.go
@@ -94,7 +94,7 @@
 // contain every file in buildFilesDir and srcDir excluding the files in
 // exclude. Collects every directory encountered during the traversal of srcDir
 // into acc.
-func plantSymlinkForestRecursive(topdir string, forestDir string, buildFilesDir string, srcDir string, exclude *node, acc *[]string) {
+func plantSymlinkForestRecursive(topdir string, forestDir string, buildFilesDir string, srcDir string, exclude *node, acc *[]string, okay *bool) {
 	if exclude != nil && exclude.excluded {
 		// This directory is not needed, bail out
 		return
@@ -149,7 +149,7 @@
 			if buildFilesChildEntry.IsDir() && excludeChild != nil {
 				// Not in the source tree, but we have to exclude something from under
 				// this subtree, so descend
-				plantSymlinkForestRecursive(topdir, forestChild, buildFilesChild, srcChild, excludeChild, acc)
+				plantSymlinkForestRecursive(topdir, forestChild, buildFilesChild, srcChild, excludeChild, acc, okay)
 			} else {
 				// Not in the source tree, symlink BUILD file
 				symlinkIntoForest(topdir, forestChild, buildFilesChild)
@@ -158,20 +158,26 @@
 			if srcChildEntry.IsDir() && excludeChild != nil {
 				// Not in the build file tree, but we have to exclude something from
 				// under this subtree, so descend
-				plantSymlinkForestRecursive(topdir, forestChild, buildFilesChild, srcChild, excludeChild, acc)
+				plantSymlinkForestRecursive(topdir, forestChild, buildFilesChild, srcChild, excludeChild, acc, okay)
 			} else {
 				// Not in the build file tree, symlink source tree, carry on
 				symlinkIntoForest(topdir, forestChild, srcChild)
 			}
 		} else if srcChildEntry.IsDir() && buildFilesChildEntry.IsDir() {
 			// Both are directories. Descend.
-			plantSymlinkForestRecursive(topdir, forestChild, buildFilesChild, srcChild, excludeChild, acc)
+			plantSymlinkForestRecursive(topdir, forestChild, buildFilesChild, srcChild, excludeChild, acc, okay)
+		} else if !srcChildEntry.IsDir() && !buildFilesChildEntry.IsDir() {
+			// Neither is a directory. Prioritize BUILD files generated by bp2build
+			// over any BUILD file imported into external/.
+			fmt.Fprintf(os.Stderr, "Both '%s' and '%s' exist, symlinking the former to '%s'\n",
+				buildFilesChild, srcChild, forestChild)
+			symlinkIntoForest(topdir, forestChild, buildFilesChild)
 		} else {
 			// Both exist and one is a file. This is an error.
 			fmt.Fprintf(os.Stderr,
-				"Conflict in workspace symlink tree creation: both '%s' and '%s' exist and at least one of them is a file\n",
+				"Conflict in workspace symlink tree creation: both '%s' and '%s' exist and exactly one is a directory\n",
 				srcChild, buildFilesChild)
-			os.Exit(1)
+			*okay = false
 		}
 	}
 }
@@ -184,6 +190,10 @@
 	deps := make([]string, 0)
 	os.RemoveAll(shared.JoinPath(topdir, forest))
 	excludeTree := treeFromExcludePathList(exclude)
-	plantSymlinkForestRecursive(topdir, forest, buildFiles, srcDir, excludeTree, &deps)
+	okay := true
+	plantSymlinkForestRecursive(topdir, forest, buildFiles, srcDir, excludeTree, &deps, &okay)
+	if !okay {
+		os.Exit(1)
+	}
 	return deps
 }