diff --git a/src/comp/Makefile b/src/comp/Makefile
index ae8828b01..ac57e3e55 100644
--- a/src/comp/Makefile
+++ b/src/comp/Makefile
@@ -81,8 +81,8 @@ GHCPATCH=$(shell echo $(GHCVERSION) | cut -d. -f3)
 ifeq ($(GHCMAJOR),9)
 
 # Warn about newer versions that are not yet supported
-GHCMINORGT8 := $(shell expr $(GHCMINOR) \> 8)
-ifeq ($(GHCMINORGT8),1)
+GHCMINORGT10 := $(shell expr $(GHCMINOR) \> 10)
+ifeq ($(GHCMINORGT10),1)
 $(warning Unsupported GHC 9 minor version: $(GHCMINOR))
 endif
 
diff --git a/src/vendor/htcl/Makefile b/src/vendor/htcl/Makefile
index 221f4711e..87d926795 100644
--- a/src/vendor/htcl/Makefile
+++ b/src/vendor/htcl/Makefile
@@ -7,7 +7,9 @@ include $(TOP)/platform.mk
 
 TCLVER=$(shell echo 'catch { puts [info tclversion]; exit 0}; exit 1' | $(TCLSH))
 ifeq ($(TCLVER),8.5)
-GHCFLAGS += -DTCL85
+# Use -optc-D instead of -D, since not all versions of GHC pass -D to the C compiler
+# (see GHC issue 24885)
+GHCFLAGS += -optc-DTCL85
 else
 ifeq ($(TCLVER),8.6)
 # No flags needed