diff --git a/libc/decl/errno_values.h b/libc/decl/errno_values.h
index 84ff6c5e..939468d5 100644
--- a/libc/decl/errno_values.h
+++ b/libc/decl/errno_values.h
@@ -70,6 +70,7 @@
 #define ENOMSG 78
 #define ENOPROTOOPT 79
 #define ENOTCONN 80
+#define EDEADLK 81
 
 #define EOPNOTSUPP ENOTSUP
 
diff --git a/libc/strerror.cpp b/libc/strerror.cpp
index ffaaba95..71058284 100644
--- a/libc/strerror.cpp
+++ b/libc/strerror.cpp
@@ -99,6 +99,7 @@ extern "C" const char* sortix_strerror(int errnum)
 	case ENOMSG: return "No message of the desired type";
 	case ENOPROTOOPT: return "Protocol not available";
 	case ENOTCONN: return "Socket is not connected";
+	case EDEADLK: return "Resource deadlock avoided";
 	default: return "Unknown error condition";
 	}
 }