diff --git a/include/light/light.hh b/include/light/light.hh
index 869832fb..09a6c5d6 100644
--- a/include/light/light.hh
+++ b/include/light/light.hh
@@ -222,11 +222,15 @@ protected:
     bool _locked;
     bool _registered;
     std::vector<std::string> _names;
-
-public:
-    const std::vector<std::string> &names() const { return _names; }
+    
     lockable_setting_t(std::vector<std::string> names)
-    : _locked(false), _registered(false), _names(names) {}
+    : _locked(false), _registered(false), _names(names) {
+        assert(_names.size() > 0);
+    }
+    
+public:
+    const std::string &primaryName() const { return _names.at(0); }
+    const std::vector<std::string> &names() const { return _names; }
     
     bool isRegistered() { return _registered; }
     void setRegistered() { _registered = true; }
@@ -234,7 +238,22 @@ public:
 
 class lockable_vec_t : public lockable_setting_t {
 private:
-    vec_t _value;
+    float _value, _min, _max;
+    
+    void setFloatInternal(float f) {
+        assert(_registered);
+        if (f < _min) {
+            logprint("WARNING: '%s': %f is less than minimum value %f.\n",
+                     primaryName().c_str(), f, _min);
+            f = _min;
+        }
+        if (f > _max) {
+            logprint("WARNING: '%s': %f is greater than maximum value %f.\n",
+                     primaryName().c_str(), f, _max);
+            f = _max;
+        }
+        _value = f;
+    }
     
 public:
     bool boolValue() const {
@@ -250,23 +269,30 @@ public:
     }
     
     void setFloatValue(float f) {
-        assert(_registered);
         if (!_locked) {
-            _value = f;
+            setFloatInternal(f);
         }
     }
     
     void setFloatValueLocked(float f) {
-        assert(_registered);
-        _value = f;
+        setFloatInternal(f);
         _locked = true;
     }
     
-    lockable_vec_t(std::vector<std::string> names, vec_t v)
-    : lockable_setting_t(names), _value(v) {}
+    lockable_vec_t(std::vector<std::string> names, float v,
+                   float minval=-std::numeric_limits<float>::infinity(),
+                   float maxval=std::numeric_limits<float>::infinity())
+    : lockable_setting_t(names), _value(v), _min(minval), _max(maxval) {
+        // check the default value is valid
+        assert(_min < _max);
+        assert(_value >= _min);
+        assert(_value <= _max);
+    }
     
-    lockable_vec_t(std::string name, vec_t v)
-    : lockable_vec_t(std::vector<std::string> { name }, v) {}
+    lockable_vec_t(std::string name, float v,
+                   float minval=-std::numeric_limits<float>::infinity(),
+                   float maxval=std::numeric_limits<float>::infinity())
+    : lockable_vec_t(std::vector<std::string> { name }, v, minval, maxval) {}
 };
 
 class lockable_vec3_t : public lockable_setting_t {
diff --git a/light/entities.cc b/light/entities.cc
index 8bf919de..aead0e80 100644
--- a/light/entities.cc
+++ b/light/entities.cc
@@ -52,7 +52,7 @@ lockable_vec_t sunlight_dirt    { "sunlight_dirt", 0.0f };
 lockable_vec_t sunlight2_dirt   { "sunlight2_dirt", 0.0f };
 lockable_vec3_t sunvec          { strings{"sunlight_mangle", "sun_mangle"}, 0.0f, 0.0f, -1.0f };  /* defaults to straight down */
 lockable_vec3_t sun2vec         { "sun2_mangle", 0.0f, 0.0f, -1.0f };  /* defaults to straight down */
-lockable_vec_t sun_deviance     { "sunlight_penumbra", 0.0f };
+lockable_vec_t sun_deviance     { "sunlight_penumbra", 0.0f, 0.0f, 180.0f };
 
 // entity_t
 
diff --git a/light/light.cc b/light/light.cc
index a91056d3..46e2b59c 100644
--- a/light/light.cc
+++ b/light/light.cc
@@ -43,12 +43,12 @@ using namespace std;
 
 using strings = std::vector<std::string>;
 
-lockable_vec_t scaledist {"dist", 1.0};
-lockable_vec_t rangescale {"range", 0.5};
-lockable_vec_t global_anglescale {strings{"anglescale", "anglesense"}, 0.5};
+lockable_vec_t scaledist {"dist", 1.0, 0.0f, 100.0f};
+lockable_vec_t rangescale {"range", 0.5f, 0.0f, 100.0f};
+lockable_vec_t global_anglescale {strings{"anglescale", "anglesense"}, 0.5, 0.0f, 1.0f};
 float fadegate = EQUAL_EPSILON;
 int softsamples = 0;
-lockable_vec_t lightmapgamma {"gamma", 1.0};
+lockable_vec_t lightmapgamma {"gamma", 1.0, 0.0f, 100.0f};
 const vec3_t vec3_white = { 255, 255, 255 };
 float surflight_subdivide = 128.0f;
 int sunsamples = 64;
@@ -63,10 +63,10 @@ sun_t *suns = NULL;
 /* dirt */
 lockable_vec_t dirty {strings{"dirt", "dirty"}, 0.0f};
 lockable_vec_t dirtMode {"dirtmode", 0.0f};
-lockable_vec_t dirtDepth {"dirtdepth", 128.0f};
-lockable_vec_t dirtScale {"dirtscale", 1.0f};
-lockable_vec_t dirtGain {"dirtgain", 1.0f};
-lockable_vec_t dirtAngle {"dirtangle", 88.0f};
+lockable_vec_t dirtDepth {"dirtdepth", 128.0f, 1.0f, std::numeric_limits<float>::infinity()};
+lockable_vec_t dirtScale {"dirtscale", 1.0f, 0.0f, 100.0f};
+lockable_vec_t dirtGain {"dirtgain", 1.0f, 0.0f, 100.0f};
+lockable_vec_t dirtAngle {"dirtangle", 88.0f, 0.0f, 90.0f};
 
 qboolean globalDirt = false;
 lockable_vec_t minlightDirt {"minlight_dirt", 0};
@@ -76,8 +76,8 @@ lockable_vec_t phongallowed {"phong", 1.0f};
 
 /* bounce */
 lockable_vec_t bounce {"bounce", 0.0f};
-lockable_vec_t bouncescale {"bouncescale", 1.0f};
-lockable_vec_t bouncecolorscale {"bouncecolorscale", 0.0f};
+lockable_vec_t bouncescale {"bouncescale", 1.0f, 0.0f, 100.0f};
+lockable_vec_t bouncecolorscale {"bouncecolorscale", 0.0f, 0.0f, 1.0f};
 
 qboolean surflight_dump = false;