diff --git a/test/sharness/lib/test-lib.sh b/test/sharness/lib/test-lib.sh
index e478cd08625..bed6b44c714 100644
--- a/test/sharness/lib/test-lib.sh
+++ b/test/sharness/lib/test-lib.sh
@@ -45,7 +45,9 @@ test "$TEST_EXPENSIVE" = 1 && test_set_prereq EXPENSIVE
 test "$TEST_NO_DOCKER" != 1 && type docker && test_set_prereq DOCKER
 
 TEST_OS=$(uname -s | tr [a-z] [A-Z])
-test expr "$TEST_OS" : "CYGWIN_NT" >/dev/null && test_set_prereq POSIX
+
+# Set a prereq as error messages are often different on Windows/Cygwin
+expr "$TEST_OS" : "CYGWIN_NT" >/dev/null || test_set_prereq STD_ERR_MSG
 
 if test "$TEST_VERBOSE" = 1; then
 	echo '# TEST_VERBOSE='"$TEST_VERBOSE"
diff --git a/test/sharness/t0020-init.sh b/test/sharness/t0020-init.sh
index 135ebab4999..7bb98f0dd9a 100755
--- a/test/sharness/t0020-init.sh
+++ b/test/sharness/t0020-init.sh
@@ -19,8 +19,16 @@ test_expect_success "ipfs init fails" '
 	test_must_fail ipfs init 2> init_fail_out
 '
 
-test_expect_success POSIX "ipfs init output looks good" '
-	echo "Error: failed to take lock at $IPFS_PATH: permission denied" > init_fail_exp &&
+# Under Windows/Cygwin the error message is different,
+# so we use the STD_ERR_MSG prereq.
+if test_have_prereq STD_ERR_MSG; then
+	init_err_msg="Error: failed to take lock at $IPFS_PATH: permission denied"
+else
+	init_err_msg="Error: mkdir $IPFS_PATH: The system cannot find the path specified."
+fi
+
+test_expect_success "ipfs init output looks good" '
+	echo "$init_err_msg" >init_fail_exp &&
 	test_cmp init_fail_exp init_fail_out
 '