diff --git a/dlls/api-ms-win-crt-convert-l1-1-0/api-ms-win-crt-convert-l1-1-0.spec b/dlls/api-ms-win-crt-convert-l1-1-0/api-ms-win-crt-convert-l1-1-0.spec
index 1b877e38728..06acf25e9d7 100644
--- a/dlls/api-ms-win-crt-convert-l1-1-0/api-ms-win-crt-convert-l1-1-0.spec
+++ b/dlls/api-ms-win-crt-convert-l1-1-0/api-ms-win-crt-convert-l1-1-0.spec
@@ -33,7 +33,7 @@
 @ cdecl _strtof_l(str ptr ptr) ucrtbase._strtof_l
 @ cdecl -ret64 _strtoi64(str ptr long) ucrtbase._strtoi64
 @ cdecl -ret64 _strtoi64_l(str ptr long ptr) ucrtbase._strtoi64_l
-@ stub _strtoimax_l
+@ cdecl -ret64 _strtoimax_l(str ptr long ptr) ucrtbase._strtoimax_l
 @ cdecl _strtol_l(str ptr long ptr) ucrtbase._strtol_l
 @ stub _strtold_l
 @ cdecl -ret64 _strtoll_l(str ptr long ptr) ucrtbase._strtoll_l
@@ -94,7 +94,7 @@
 @ cdecl mbtowc(ptr str long) ucrtbase.mbtowc
 @ cdecl strtod(str ptr) ucrtbase.strtod
 @ cdecl strtof(str ptr) ucrtbase.strtof
-@ stub strtoimax
+@ cdecl -ret64 strtoimax(str ptr long) ucrtbase.strtoimax
 @ cdecl strtol(str ptr long) ucrtbase.strtol
 @ stub strtold
 @ cdecl -ret64 strtoll(str ptr long) ucrtbase.strtoll
diff --git a/dlls/ucrtbase/ucrtbase.spec b/dlls/ucrtbase/ucrtbase.spec
index 0d7616c45c8..a47c8ff7956 100644
--- a/dlls/ucrtbase/ucrtbase.spec
+++ b/dlls/ucrtbase/ucrtbase.spec
@@ -1952,7 +1952,7 @@
 @ cdecl _strtof_l(str ptr ptr) MSVCRT__strtof_l
 @ cdecl -ret64 _strtoi64(str ptr long) MSVCRT_strtoi64
 @ cdecl -ret64 _strtoi64_l(str ptr long ptr) MSVCRT_strtoi64_l
-@ stub _strtoimax_l
+@ cdecl -ret64 _strtoimax_l(str ptr long ptr) MSVCRT_strtoi64_l
 @ cdecl _strtol_l(str ptr long ptr) MSVCRT__strtol_l
 @ stub _strtold_l
 @ cdecl -ret64 _strtoll_l(str ptr long ptr) MSVCRT_strtoi64_l
@@ -2518,7 +2518,7 @@
 @ cdecl strstr(str str) MSVCRT_strstr
 @ cdecl strtod(str ptr) MSVCRT_strtod
 @ cdecl strtof(str ptr) MSVCRT_strtof
-@ stub strtoimax
+@ cdecl -ret64 strtoimax(str ptr long) MSVCRT_strtoi64
 @ cdecl strtok(str str) MSVCRT_strtok
 @ cdecl strtok_s(ptr str ptr) MSVCRT_strtok_s
 @ cdecl strtol(str ptr long) MSVCRT_strtol