diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9fb0f966..c7855973 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@ Version 1.2.4
 -------------
 
 - Removed broken remote combinator signaling.
+- Fixed research sync endlessly updating already researched technologies
 
 
 Version 1.2.3
diff --git a/sharedPlugins/researchSync/index.js b/sharedPlugins/researchSync/index.js
index 1a0cdd7d..70244053 100644
--- a/sharedPlugins/researchSync/index.js
+++ b/sharedPlugins/researchSync/index.js
@@ -284,6 +284,11 @@ class ResearchSync {
             if (isNaN(cluster_techs[name].progress))
                 continue
 
+			// Ignore researched techs
+			if (!tech.infinite && tech.researched) {
+				continue;
+			}
+
 			// Do not update progress for infinite techs with a local level that's higher.
 			if (tech.infinite && tech.level > cluster_techs[name].level) {
 				continue;