diff --git a/docs/examples/Makefile.m32 b/docs/examples/Makefile.m32
index 160afb62f..dd989a8fb 100644
--- a/docs/examples/Makefile.m32
+++ b/docs/examples/Makefile.m32
@@ -106,7 +106,7 @@ CFLAGS += -fno-strict-aliasing
 # comment LDFLAGS below to keep debug info
 LDFLAGS = $(CURL_LDFLAG_EXTRAS) $(CURL_LDFLAG_EXTRAS_EXE) -s
 RC = $(CROSSPREFIX)windres
-RCFLAGS = --include-dir=$(PROOT)/include -O COFF
+RCFLAGS = --include-dir=$(PROOT)/include -O coff
 
 # Set environment var ARCH to your architecture to override autodetection.
 ifndef ARCH
diff --git a/lib/Makefile.m32 b/lib/Makefile.m32
index ac6b3de63..fe8701bdb 100644
--- a/lib/Makefile.m32
+++ b/lib/Makefile.m32
@@ -99,7 +99,7 @@ LDFLAGS = $(CURL_LDFLAG_EXTRAS) $(CURL_LDFLAG_EXTRAS_DLL) -s
 AR = $(CURL_AR)
 RANLIB = $(CURL_RANLIB)
 RC = $(CROSSPREFIX)windres
-RCFLAGS = --include-dir=$(PROOT)/include -DDEBUGBUILD=0 -O COFF
+RCFLAGS = --include-dir=$(PROOT)/include -DDEBUGBUILD=0 -O coff
 STRIP   = $(CROSSPREFIX)strip -g
 
 # Set environment var ARCH to your architecture to override autodetection.
diff --git a/src/Makefile.m32 b/src/Makefile.m32
index e13db04b9..f34d96437 100644
--- a/src/Makefile.m32
+++ b/src/Makefile.m32
@@ -107,7 +107,7 @@ CFLAGS += -fno-strict-aliasing
 LDFLAGS = $(CURL_LDFLAG_EXTRAS) $(CURL_LDFLAG_EXTRAS_EXE) -s
 AR = $(CURL_AR)
 RC = $(CROSSPREFIX)windres
-RCFLAGS = --include-dir=$(PROOT)/include -O COFF -DCURL_EMBED_MANIFEST
+RCFLAGS = --include-dir=$(PROOT)/include -O coff -DCURL_EMBED_MANIFEST
 STRIP   = $(CROSSPREFIX)strip -g
 
 # We may need these someday