diff --git a/soundlib/plugins/dmo/I3DL2Reverb.cpp b/soundlib/plugins/dmo/I3DL2Reverb.cpp
index d7cbea8a636..10440868e51 100644
--- a/soundlib/plugins/dmo/I3DL2Reverb.cpp
+++ b/soundlib/plugins/dmo/I3DL2Reverb.cpp
@@ -505,7 +505,7 @@ void I3DL2Reverb::RecalculateI3DL2ReverbParams()
 		m_roomFilter = 0.0f;
 	} else
 	{
-		float freq = std::cos(HFReference() * (2.0f * mpt::numbers::pi_v<float>) / m_effectiveSampleRate);
+		float freq = std::min(std::cos(HFReference() * (2.0f * mpt::numbers::pi_v<float>) / m_effectiveSampleRate), 0.9999f);
 		float roomFilter = (freq * (roomHF + roomHF) - 2.0f + std::sqrt(freq * (roomHF * roomHF * freq * 4.0f) + roomHF * 8.0f - roomHF * roomHF * 4.0f - roomHF * freq * 8.0f)) / (roomHF + roomHF - 2.0f);
 		m_roomFilter = Clamp(roomFilter, 0.0f, 1.0f);
 	}