diff --git a/core/deco.c b/core/deco.c
index 5d4a18c13..09426bd0a 100644
--- a/core/deco.c
+++ b/core/deco.c
@@ -248,11 +248,13 @@ double tissue_tolerance_calc(const struct dive *dive, double pressure)
 	double lowest_ceiling = 0.0;
 	double tissue_lowest_ceiling[16];
 
+	for (ci = 0; ci < 16; ci++) {
+		buehlmann_inertgas_a[ci] = ((buehlmann_N2_a[ci] * tissue_n2_sat[ci]) + (buehlmann_He_a[ci] * tissue_he_sat[ci])) / tissue_inertgas_saturation[ci];
+		buehlmann_inertgas_b[ci] = ((buehlmann_N2_b[ci] * tissue_n2_sat[ci]) + (buehlmann_He_b[ci] * tissue_he_sat[ci])) / tissue_inertgas_saturation[ci];
+	}
+
 	if (prefs.deco_mode != VPMB) {
 		for (ci = 0; ci < 16; ci++) {
-			buehlmann_inertgas_a[ci] = ((buehlmann_N2_a[ci] * tissue_n2_sat[ci]) + (buehlmann_He_a[ci] * tissue_he_sat[ci])) / tissue_inertgas_saturation[ci];
-			buehlmann_inertgas_b[ci] = ((buehlmann_N2_b[ci] * tissue_n2_sat[ci]) + (buehlmann_He_b[ci] * tissue_he_sat[ci])) / tissue_inertgas_saturation[ci];
-
 
 			/* tolerated = (tissue_inertgas_saturation - buehlmann_inertgas_a) * buehlmann_inertgas_b; */