diff --git a/src/disk_instability.cpp b/src/disk_instability.cpp
index a883f8c7..064ab2bc 100644
--- a/src/disk_instability.cpp
+++ b/src/disk_instability.cpp
@@ -188,9 +188,11 @@ void DiskInstability::create_starburst(SubhaloPtr &subhalo, GalaxyPtr &galaxy, d
 		// Define accretion rate.
 		galaxy->smbh.macc_sb = delta_mbh/tdyn;
 
-		// Grow SMBH.
-		galaxy->smbh.mass += delta_mbh;
-		galaxy->smbh.mass_metals += delta_mzbh;
+		// Check if SMBH exists in this galaxy, then grow it.
+		if(galaxy->smbh.mass != 0){
+			galaxy->smbh.mass += delta_mbh;
+			galaxy->smbh.mass_metals += delta_mzbh;
+		}
 
 		// Reduce gas available for star formation due to black hole growth.
 		galaxy->bulge_gas.mass -= delta_mbh;
diff --git a/src/galaxy_mergers.cpp b/src/galaxy_mergers.cpp
index 8e85f614..0f3a6440 100644
--- a/src/galaxy_mergers.cpp
+++ b/src/galaxy_mergers.cpp
@@ -540,8 +540,11 @@ void GalaxyMergers::create_starbursts(HaloPtr &halo, double z, double delta_t){
 				physicalmodel->evolve_galaxy_starburst(*subhalo, *galaxy, z, delta_t, true);
 
 				// Grow SMBH after starbursts, as during it we need a realistical measurement of Ledd the BH had before the starburst.
-				galaxy->smbh.mass += delta_mbh;
-				galaxy->smbh.mass_metals += delta_mzbh;
+				// Check if SMBH exists in this galaxy, then grow it.
+				if(galaxy->smbh.mass != 0){
+					galaxy->smbh.mass += delta_mbh;
+					galaxy->smbh.mass_metals += delta_mzbh;
+				}
 
 				// Check for small gas reservoirs left in the bulge, in case mass is small, transfer to disk.
 				if(galaxy->bulge_gas.mass > 0 && galaxy->bulge_gas.mass < parameters.mass_min){