diff --git a/core/deco.c b/core/deco.c
index 33a049f7c..469679684 100644
--- a/core/deco.c
+++ b/core/deco.c
@@ -321,46 +321,34 @@ double tissue_tolerance_calc(const struct dive *dive, double pressure)
 /*
  * Return buelman factor for a particular period and tissue index.
  *
- * We cache the last factor, since we commonly call this with the
+ * We cache the factor, since we commonly call this with the
  * same values... We have a special "fixed cache" for the one second
  * case, although I wonder if that's even worth it considering the
  * more general-purpose cache.
  */
-struct factor_cache {
-	int last_period;
-	double last_factor;
-};
 
-double n2_factor(int period_in_seconds, int ci)
+
+double factor(int period_in_seconds, int ci, enum inertgas gas)
 {
-	static struct factor_cache cache[16];
-
-	if (period_in_seconds == 1)
-		return buehlmann_N2_factor_expositon_one_second[ci];
-
-	if (period_in_seconds != cache[ci].last_period) {
-		cache[ci].last_period = period_in_seconds;
-		// ln(2)/60 = 1.155245301e-02
-		cache[ci].last_factor = 1 - exp(-period_in_seconds * 1.155245301e-02 / buehlmann_N2_t_halflife[ci]);
+	double factor;
+	if (period_in_seconds == 1) {
+		if (gas == N2)
+			return buehlmann_N2_factor_expositon_one_second[ci];
+		else
+			return buehlmann_He_factor_expositon_one_second[ci];
 	}
 
-	return cache[ci].last_factor;
-}
-
-double he_factor(int period_in_seconds, int ci)
-{
-	static struct factor_cache cache[16];
-
-	if (period_in_seconds == 1)
-		return buehlmann_He_factor_expositon_one_second[ci];
-
-	if (period_in_seconds != cache[ci].last_period) {
-		cache[ci].last_period = period_in_seconds;
+	factor = cache_value(ci, period_in_seconds, gas);
+	if (!factor) {
 		// ln(2)/60 = 1.155245301e-02
-		cache[ci].last_factor = 1 - exp(-period_in_seconds * 1.155245301e-02 / buehlmann_He_t_halflife[ci]);
+		if (gas == N2)
+			factor = 1 - exp(-period_in_seconds * 1.155245301e-02 / buehlmann_N2_t_halflife[ci]);
+		else
+			factor = 1 - exp(-period_in_seconds * 1.155245301e-02 / buehlmann_He_t_halflife[ci]);
+		cache_insert(ci, period_in_seconds, gas, factor);
 	}
 
-	return cache[ci].last_factor;
+	return factor;
 }
 
 double calc_surface_phase(double surface_pressure, double he_pressure, double n2_pressure, double he_time_constant, double n2_time_constant)
@@ -515,8 +503,8 @@ void add_segment(double pressure, const struct gasmix *gasmix, int period_in_sec
 	for (ci = 0; ci < 16; ci++) {
 		double pn2_oversat = pressures.n2 - deco_state->tissue_n2_sat[ci];
 		double phe_oversat = pressures.he - deco_state->tissue_he_sat[ci];
-		double n2_f = n2_factor(period_in_seconds, ci);
-		double he_f = he_factor(period_in_seconds, ci);
+		double n2_f = factor(period_in_seconds, ci, N2);
+		double he_f = factor(period_in_seconds, ci, HE);
 		double n2_satmult = pn2_oversat > 0 ? buehlmann_config.satmult : buehlmann_config.desatmult;
 		double he_satmult = phe_oversat > 0 ? buehlmann_config.satmult : buehlmann_config.desatmult;
 
diff --git a/core/planner.c b/core/planner.c
index 9bf0436a0..61022d914 100644
--- a/core/planner.c
+++ b/core/planner.c
@@ -627,7 +627,6 @@ int wait_until(struct dive *dive, int clock, int min, int leap, int stepsize, in
 {
 	// Round min + leap up to the next multiple of stepsize
 	int upper = min + leap + stepsize - 1 - (min + leap - 1) % stepsize;
-	printf("clock: %d min: %d leap: %d, depth %d\n", clock / 60, min / 60, leap, depth);
 	// Is the upper boundary too small?
 	if (!trial_ascent(upper - clock, depth, target_depth, avg_depth, bottom_time, gasmix, po2, surface_pressure, dive))
 		return wait_until(dive, clock, upper, leap, stepsize, depth, target_depth, avg_depth, bottom_time, gasmix, po2, surface_pressure);
diff --git a/core/qthelper.cpp b/core/qthelper.cpp
index b9698e6b8..e6a4e056a 100644
--- a/core/qthelper.cpp
+++ b/core/qthelper.cpp
@@ -1710,3 +1710,21 @@ char *intdup(int index)
 	tmpbuf[20] = 0;
 	return strdup(tmpbuf);
 }
+
+QHash<int, double> factor_cache;
+
+extern "C" double cache_value(int tissue, int timestep, enum inertgas inertgas)
+{
+	int key = (timestep << 5) + (tissue << 1);
+	if (inertgas == HE)
+		++key;
+	return factor_cache.value(key);
+}
+
+extern "C" void cache_insert(int tissue, int timestep, enum inertgas inertgas, double value)
+{
+	int key = (timestep << 5) + (tissue << 1);
+	if (inertgas == HE)
+		++key;
+	factor_cache.insert(key, value);
+}
diff --git a/core/qthelper.h b/core/qthelper.h
index ff91b771a..ac91fbc1e 100644
--- a/core/qthelper.h
+++ b/core/qthelper.h
@@ -49,5 +49,8 @@ QString getUUID();
 QStringList imageExtensionFilters();
 char *intdup(int index);
 extern "C" int parse_seabear_header(const char *filename, char **params, int pnr);
+enum inertgas {N2, HE};
+extern "C" double cache_value(int tissue, int timestep, enum inertgas gas);
+extern "C" void cache_insert(int tissue, int timestep, enum inertgas gas, double value);
 
 #endif // QTHELPER_H
diff --git a/core/qthelperfromc.h b/core/qthelperfromc.h
index 3ea18e7cf..dc09e224b 100644
--- a/core/qthelperfromc.h
+++ b/core/qthelperfromc.h
@@ -22,6 +22,8 @@ const char *subsurface_user_agent();
 enum deco_mode decoMode();
 int parse_seabear_header(const char *filename, char **params, int pnr);
 extern const char *get_current_date();
-
+enum inertgas {N2, HE};
+double cache_value(int tissue, int timestep, enum inertgas gas);
+void cache_insert(int tissue, int timestep, enum inertgas gas, double value);
 
 #endif // QTHELPERFROMC_H