diff --git a/Makefile b/Makefile
index eb95164c..46541063 100644
--- a/Makefile
+++ b/Makefile
@@ -151,6 +151,12 @@ endif
 
 # Guess the compiler's XLEN
 OPENSBI_CC_XLEN := $(shell TMP=`$(CC) $(CLANG_TARGET) -dumpmachine | sed 's/riscv\([0-9][0-9]\).*/\1/'`; echo $${TMP})
+# If guessing XLEN fails, default to 64
+ifneq ($(OPENSBI_CC_XLEN),32)
+  ifneq ($(OPENSBI_CC_XLEN),64)
+    OPENSBI_CC_XLEN = 64
+  endif
+endif
 
 # Guess the compiler's ABI and ISA
 ifneq ($(CC_IS_CLANG),y)