diff --git a/libc/include/errno.h b/libc/include/errno.h
index 9ad0f589..84a75fbe 100644
--- a/libc/include/errno.h
+++ b/libc/include/errno.h
@@ -104,6 +104,7 @@ __BEGIN_DECLS
 #define ENOLCK 84
 #define ENOUSER 85
 #define ENOGROUP 86
+#define ESIGPENDING 87
 
 #define EOPNOTSUPP ENOTSUP
 
diff --git a/libc/string/strerror.cpp b/libc/string/strerror.cpp
index 2be1df79..7673abfb 100644
--- a/libc/string/strerror.cpp
+++ b/libc/string/strerror.cpp
@@ -105,6 +105,7 @@ extern "C" const char* sortix_strerror(int errnum)
 	case ENOLCK: return "No locks available";
 	case ENOUSER: return "No such user";
 	case ENOGROUP: return "No such group";
+	case ESIGPENDING: return "Signal is already pending";
 	default: return "Unknown error condition";
 	}
 }