diff --git a/ConfigureChecks.cmake b/ConfigureChecks.cmake
index e4d0e2ec..bba33fa9 100644
--- a/ConfigureChecks.cmake
+++ b/ConfigureChecks.cmake
@@ -10,6 +10,7 @@ check_include_files(sys/utsname.h HAVE_SYS_UTSNAME_H)
 check_include_files(fcntl.h HAVE_FCNTL_H)
 check_include_files(unistd.h HAVE_UNISTD_H)
 check_include_files(wctype.h HAVE_WCTYPE_H)
+check_include_files(stdbool.h HAVE_STDBOOL_H)
 
 include(CheckFunctionExists)
 if(WIN32 AND MSVC)
diff --git a/config.h.cmake b/config.h.cmake
index 8fd3421b..c8008692 100644
--- a/config.h.cmake
+++ b/config.h.cmake
@@ -39,6 +39,9 @@
 /* Define to 1 if you have the <dirent.h> header file. */
 #cmakedefine HAVE_DIRENT_H 1
 
+/* Define to 1 if you have the <stdbool.h> header file. */
+#cmakedefine HAVE_STDBOOL_H 1
+
 /* Define if we have pthread. */
 #cmakedefine HAVE_PTHREAD_ATTR_GET_NP 1
 #cmakedefine HAVE_PTHREAD_GETATTR_NP 1
diff --git a/src/libical/icalrecur.c b/src/libical/icalrecur.c
index 38ee2bb3..64ec9732 100644
--- a/src/libical/icalrecur.c
+++ b/src/libical/icalrecur.c
@@ -145,6 +145,12 @@
 #if defined(HAVE_LIBICU)
 #include <unicode/ucal.h>
 #include <unicode/ustring.h>
+#if defined(HAVE_STDBOOL_H)
+#include <stdbool.h>
+#else
+#define false 0
+#define true 1
+#endif
 #define RSCALE_IS_SUPPORTED 1
 #else
 #define RSCALE_IS_SUPPORTED 0
@@ -1018,7 +1024,7 @@ icalarray *icalrecurrencetype_rscale_supported_calendars(void)
 
     calendars = icalarray_new(sizeof(const char **), 20);
 
-    en = ucal_getKeywordValuesForLocale("calendar", NULL, FALSE, &status);
+    en = ucal_getKeywordValuesForLocale("calendar", NULL, false, &status);
     while ((cal = uenum_next(en, NULL, &status))) {
         cal = icalmemory_tmp_copy(cal);
         icalarray_append(calendars, &cal);
@@ -1411,7 +1417,7 @@ static int initialize_rscale(icalrecur_iterator *impl)
         }
 
         /* Check if specified calendar is supported */
-        en = ucal_getKeywordValuesForLocale("calendar", NULL, FALSE, &status);
+        en = ucal_getKeywordValuesForLocale("calendar", NULL, false, &status);
         while ((cal = uenum_next(en, NULL, &status))) {
             if (!strcmp(cal, rule.rscale)) {
                 is_hebrew = !strcmp(rule.rscale, "hebrew");