diff --git a/minteq.v4.dat b/minteq.v4.dat
index 525a169c..b3ec9552 100644
--- a/minteq.v4.dat
+++ b/minteq.v4.dat
@@ -3411,7 +3411,7 @@ Mn+2 + SeO4-2 = MnSeO4
 		#T and ionic strength:	 0.00 25.0
 NH4+ = NH3 + H+
 	log_k	-9.244
-	delta_h	-52	kJ
+	delta_h	52	kJ
 	-gamma	0	0
 		#                  Id:	3304900
 		#        log K source:	NIST46.3