diff --git a/ImGuiVisitor.cpp b/ImGuiVisitor.cpp
index 4858afe..ce70ff8 100644
--- a/ImGuiVisitor.cpp
+++ b/ImGuiVisitor.cpp
@@ -489,7 +489,7 @@ void ImGuiVisitor::visit (PatternSource& s)
     ImGui::SetNextItemWidth(IMGUI_RIGHT_ALIGN);
     if (ImGui::BeginCombo("##Patterns", Pattern::pattern_types[s.pattern()->type()].c_str()) )
     {
-        for (int p = 0; p < Pattern::pattern_types.size(); ++p){
+        for (uint p = 0; p < Pattern::pattern_types.size(); ++p){
             if (ImGui::Selectable( Pattern::pattern_types[p].c_str() )) {
                 s.setPattern(p, s.pattern()->resolution());
                 std::ostringstream oss;
diff --git a/Mixer.cpp b/Mixer.cpp
index f1f37c2..74dc3a6 100644
--- a/Mixer.cpp
+++ b/Mixer.cpp
@@ -278,7 +278,7 @@ Source * Mixer::createSourceStream(const std::string &gstreamerpipeline)
     return s;
 }
 
-Source * Mixer::createSourcePattern(int pattern, glm::ivec2 res)
+Source * Mixer::createSourcePattern(uint pattern, glm::ivec2 res)
 {
     // ready to create a source
     PatternSource *s = new PatternSource;
diff --git a/Mixer.h b/Mixer.h
index da08b06..7528b40 100644
--- a/Mixer.h
+++ b/Mixer.h
@@ -40,7 +40,7 @@ public:
     Source * createSourceClone  (const std::string &namesource = "");
     Source * createSourceRender ();
     Source * createSourceStream (const std::string &gstreamerpipeline);
-    Source * createSourcePattern(int pattern, glm::ivec2 res);
+    Source * createSourcePattern(uint pattern, glm::ivec2 res);
     Source * createSourceDevice (const std::string &namedevice);
 
     // operations on sources
diff --git a/PatternSource.cpp b/PatternSource.cpp
index 66f5c76..2c0641d 100644
--- a/PatternSource.cpp
+++ b/PatternSource.cpp
@@ -11,6 +11,8 @@
 #include "Visitor.h"
 #include "Log.h"
 
+#define MAX_PATTERN 23
+
 //    smpte (0) – SMPTE 100%% color bars
 //    snow (1) – Random (television snow)
 //    black (2) – 100%% Black
@@ -88,7 +90,7 @@ std::vector<std::string> Pattern::pattern_types = { "Black",
                                          "Clock"
                                        };
 
-Pattern::Pattern() : Stream()
+Pattern::Pattern() : Stream(), type_(MAX_PATTERN+1) // invalid pattern
 {
 
 }
@@ -101,13 +103,13 @@ glm::ivec2 Pattern::resolution()
 
 void Pattern::open( uint pattern, glm::ivec2 res )
 {
-    type_ = CLAMP(pattern, 0, 23);
+    type_ = MIN(pattern, MAX_PATTERN);
     std::string gstreamer_pattern = pattern_internal_[type_];
 
     // there is always a special case...
     switch(type_)
     {
-    case 18:
+    case 18: // zone plates
     case 17:
     {
         std::ostringstream oss;
@@ -119,7 +121,7 @@ void Pattern::open( uint pattern, glm::ivec2 res )
         break;
     }
 
-    // all patterns before index are single frames (not animated)
+    // all patterns before 'SMPTE test pattern' are single frames (not animated)
     single_frame_ = type_ < 14;
 
     // (private) open stream
@@ -136,7 +138,7 @@ PatternSource::PatternSource() : StreamSource()
     overlays_[View::LAYER]->attach( new Symbol(Symbol::PATTERN, glm::vec3(0.8f, 0.8f, 0.01f)) );
 }
 
-void PatternSource::setPattern(int type, glm::ivec2 resolution)
+void PatternSource::setPattern(uint type, glm::ivec2 resolution)
 {
     Log::Notify("Creating Source with pattern '%s'", Pattern::pattern_types[type].c_str());
 
diff --git a/PatternSource.h b/PatternSource.h
index da0b4fd..0a58cb0 100644
--- a/PatternSource.h
+++ b/PatternSource.h
@@ -33,7 +33,7 @@ public:
 
     // specific interface
     Pattern *pattern() const;
-    void setPattern(int type, glm::ivec2 resolution);
+    void setPattern(uint type, glm::ivec2 resolution);
 
     glm::ivec2 icon() const override { return glm::ivec2(12, 5); }