diff --git a/GNUmakefile b/GNUmakefile
index 3d446d2033..eaf92a12b9 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -65,3 +65,9 @@ listings: $(wildcard Cubical/**/*.agda)
 clean:
 	find . -type f -name '*.agdai' -delete
 
+.PHONY: debug
+debug : ## Print debug information.
+	@echo "AGDA_BIN              = $(AGDA_BIN)"
+	@echo "AGDA_FLAGS            = $(AGDA_FLAGS)"
+	@echo "AGDA_EXEC             = $(AGDA_EXEC)"
+	@echo "AGDA                  = $(AGDA)"