diff --git a/Makefile b/Makefile
index 5760f73..5ee6d20 100644
--- a/Makefile
+++ b/Makefile
@@ -140,7 +140,9 @@ graph.svg: Makefile
 #         dependencies (ie. the dependency graph is a DAG);
 $(OBJDIR)/%.d: $(SRCDIR)/%.f90 | $(OBJDIR)
 	@printf '$(@:d=o): $< \\\n' > $@
-	@sed -n 's@^[^!].*use \([^,]\+\),.*@$(OBJDIR)/\1.o \\@p' '$<' | sort -u >> $@
+	@grep -v 'use iso_' '$<' | \
+	 sed -n 's@^[^!].*use \([^,]\+\),.*@$(OBJDIR)/\1.o \\@p' | \
+	 sort -u >> $@
 
 # Load the generated rules
 include $(DEPS)