diff --git a/src/simulation/elements/RFRG.cpp b/src/simulation/elements/RFRG.cpp
index c5741b686..7bf792b45 100644
--- a/src/simulation/elements/RFRG.cpp
+++ b/src/simulation/elements/RFRG.cpp
@@ -49,6 +49,11 @@ int Element_RFRG::update(UPDATE_FUNC_ARGS)
 {
 	float new_pressure = sim->pv[y/CELL][x/CELL];
 	float *old_pressure = (float *)&parts[i].tmp;
+	if (std::isnan(*old_pressure))
+	{
+		*old_pressure = new_pressure;
+		return 0;
+	}
 	
 	// * 0 bar seems to be pressure value -256 in TPT, see Air.cpp. Also, 1 bar seems to be pressure value 0.
 	//   With those two values we can set up our pressure scale which states that ... the highest pressure