diff --git a/inc/fuse/winfsp_fuse.h b/inc/fuse/winfsp_fuse.h
index 4da6b6e6..cc5d7fde 100644
--- a/inc/fuse/winfsp_fuse.h
+++ b/inc/fuse/winfsp_fuse.h
@@ -138,6 +138,11 @@ struct fuse_statvfs
 
 #define FSP_FUSE_ENV_INIT               { 'C', malloc, free }
 
+/*
+ * Note that long is 8 bytes long in Cygwin64 and 4 bytes long in Win64.
+ * For this reason we avoid using long anywhere in these headers.
+ */
+
 #else
 #error unsupported environment
 #endif
diff --git a/src/dll/fuse/fuse_opt.c b/src/dll/fuse/fuse_opt.c
index 3ee521ba..59d58653 100644
--- a/src/dll/fuse/fuse_opt.c
+++ b/src/dll/fuse/fuse_opt.c
@@ -23,11 +23,11 @@
 #define fsp_fuse_opt_match_exact        ((const char *)1)   /* exact option match */
 #define fsp_fuse_opt_match_next         ((const char *)2)   /* option match, value is next arg */
 
-#if 1
-typedef long int strtoint_result_t;
+#if defined(_WIN64)
+typedef long long strtoint_result_t;
 #else
 /* cannot use long long in 32-bit builds because we are missing symbol __allmul */
-typedef long long int strtoint_result_t;
+typedef long strtoint_result_t;
 #endif
 
 static strtoint_result_t strtoint(const char *p, const char *endp, int base, int is_signed)
@@ -299,7 +299,17 @@ static int fsp_fuse_opt_process_arg(struct fsp_fuse_env *env,
                 else if (2 <= h)
                     VAR(data, opt, char) = (char)llv;
                 else if (1 == l)
+                {
+#if defined(_WIN64)
+                    /* long is 8 bytes long in Cygwin64 and 4 bytes long in Win64 */
+                    if ('C' == env->environment)
+                        VAR(data, opt, long long) = (long long)llv;
+                    else
+                        VAR(data, opt, long) = (long)llv;
+#else
                     VAR(data, opt, long) = (long)llv;
+#endif
+                }
                 else if (2 <= l)
                     VAR(data, opt, long long) = (long long)llv;
                 else
diff --git a/tst/winfsp-tests/fuse-opt-test.c b/tst/winfsp-tests/fuse-opt-test.c
index 2e907274..f20b8aee 100644
--- a/tst/winfsp-tests/fuse-opt-test.c
+++ b/tst/winfsp-tests/fuse-opt-test.c
@@ -303,7 +303,11 @@ void fuse_opt_parse_test(void)
     ASSERT(0 == strcmp("WwWw", data.w));
     ASSERT(1 == data.x);
     ASSERT((long)040000000001 == data.y);
-    ASSERT(((long long)0x100000001 & 0xffffffff)== data.z);
+#if defined(_WIN64)
+    ASSERT((long long)0x100000001 == data.z);
+#else
+    ASSERT(((long long)0x100000001 & 0xffffffff) == data.z);
+#endif
     ASSERT(+1234567890 == data.dec);
     ASSERT(-1234567890 == data.neg);
     ASSERT(0xABCDEF == data.hex);