diff --git a/src/management/research.c b/src/management/research.c
index 5873493565..83df0fd6a1 100644
--- a/src/management/research.c
+++ b/src/management/research.c
@@ -417,6 +417,12 @@ static void research_insert_researched(int entryIndex, int category)
 {
 	rct_research_item *researchItem, *researchItem2;
 
+	researchItem = gResearchItems;
+	// First check to make sure that entry is not already accounted for
+	for (; researchItem->entryIndex != RESEARCHED_ITEMS_END; researchItem++) {
+		if (researchItem->entryIndex == entryIndex)
+			return;
+	}
 	researchItem = gResearchItems;
 	do {
 		if (researchItem->entryIndex == RESEARCHED_ITEMS_SEPARATOR) {