diff --git a/toonz/sources/common/tparam/tdoubleparam.cpp b/toonz/sources/common/tparam/tdoubleparam.cpp
index 3c2a78d..c336b84 100644
--- a/toonz/sources/common/tparam/tdoubleparam.cpp
+++ b/toonz/sources/common/tparam/tdoubleparam.cpp
@@ -757,6 +757,9 @@ void TDoubleParam::setKeyframe(int index, const TDoubleKeyframe &k) {
     dst.m_prevType = TDoubleKeyframe::None;
   else
     dst.m_prevType = keyframes[index - 1].m_type;
+
+ if (getKeyframeCount() - 1 != index)
+    keyframes[index + 1].m_prevType = dst.m_type;
 }
 
 //---------------------------------------------------------
@@ -828,6 +831,8 @@ void TDoubleParam::setKeyframe(const TDoubleKeyframe &k) {
   else
     it->m_prevType = it[-1].m_type;
 
+  if (it + 1 != keyframes.end()) it[1].m_prevType = it->m_type;
+
   m_imp->notify(TParamChange(this, 0, 0, true, false, false));
 
   assert(it == keyframes.begin() || (it - 1)->m_frame < it->m_frame);
@@ -1148,6 +1153,8 @@ is >> m_imp->m_defaultValue;
       while (!is.eos()) {
         TDoubleKeyframe kk;
         kk.loadData(is);
+         // Throw out invalid interpolation types
+        if (kk.m_type == TDoubleKeyframe::None) continue;
         TActualDoubleKeyframe k(kk);
         k.m_expression.setGrammar(m_imp->m_grammar);
         k.m_expression.setOwnerParameter(this);