diff --git a/src/main/java/org/vibur/objectpool/ConcurrentPool.java b/src/main/java/org/vibur/objectpool/ConcurrentPool.java
index 72a37eb..eb21a03 100644
--- a/src/main/java/org/vibur/objectpool/ConcurrentPool.java
+++ b/src/main/java/org/vibur/objectpool/ConcurrentPool.java
@@ -115,10 +115,11 @@ public ConcurrentPool(ConcurrentCollection<T> available, PoolObjectFactory<T> po
      */
     public ConcurrentPool(ConcurrentCollection<T> available, PoolObjectFactory<T> poolObjectFactory,
                           int initialSize, int maxSize, boolean fair, Listener<T> listener) {
-        forbidIllegalArgument(initialSize < 0);
-        forbidIllegalArgument(maxSize < 1 || maxSize < initialSize || maxSize > MAX_ALLOWED_SIZE);
-        int availableSize = available.size();
-        forbidIllegalArgument(availableSize != 0 && availableSize != initialSize);
+		forbidIllegalArgument(initialSize < 0, String.format("Initial size %s should be >= 0", initialSize));
+		forbidIllegalArgument(maxSize < 1 || maxSize < initialSize || maxSize > MAX_ALLOWED_SIZE, String.format(
+				"maxSize %s should be between %s %s this is now not the case", maxSize, MAX_ALLOWED_SIZE, initialSize));
+		int availableSize = available.size();
+		forbidIllegalArgument(availableSize != 0 && availableSize != initialSize, String.format("availableSize == initialSize (%s != %s)", availableSize, initialSize));
 
         this.available = requireNonNull(available);
         this.poolObjectFactory = requireNonNull(poolObjectFactory);
@@ -396,7 +397,7 @@ public int maxSize() {
 
     @Override
     public int reduceCreatedBy(int reduceBy, boolean ignoreInitialSize) {
-        forbidIllegalArgument(reduceBy < 0);
+		forbidIllegalArgument(reduceBy < 0, String.format("reduceBy %s should be >= 0", reduceBy));
 
         for (int cnt = 0; cnt < reduceBy; cnt++) {
             if (!reduceByOne(ignoreInitialSize)) {
@@ -408,7 +409,7 @@ public int reduceCreatedBy(int reduceBy, boolean ignoreInitialSize) {
 
     @Override
     public int reduceCreatedTo(int reduceTo, boolean ignoreInitialSize) {
-        forbidIllegalArgument(reduceTo < 0);
+		forbidIllegalArgument(reduceTo < 0,String.format("reduceTo %s should be >= 0", reduceTo));
 
         int cnt;
         for (cnt = 0; createdTotal() > reduceTo; cnt++) {
diff --git a/src/main/java/org/vibur/objectpool/util/ArgumentValidation.java b/src/main/java/org/vibur/objectpool/util/ArgumentValidation.java
index 7066515..48f7c66 100644
--- a/src/main/java/org/vibur/objectpool/util/ArgumentValidation.java
+++ b/src/main/java/org/vibur/objectpool/util/ArgumentValidation.java
@@ -23,9 +23,9 @@ public final class ArgumentValidation {
 
     private ArgumentValidation() { }
 
-    public static void forbidIllegalArgument(boolean condition) {
+    public static void forbidIllegalArgument(boolean condition, String msg) {
         if (condition) {
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException(msg);
         }
     }
 }
diff --git a/src/main/java/org/vibur/objectpool/util/SamplingPoolReducer.java b/src/main/java/org/vibur/objectpool/util/SamplingPoolReducer.java
index 55e9cca..2ac7574 100644
--- a/src/main/java/org/vibur/objectpool/util/SamplingPoolReducer.java
+++ b/src/main/java/org/vibur/objectpool/util/SamplingPoolReducer.java
@@ -72,11 +72,11 @@ public class SamplingPoolReducer implements ThreadedPoolReducer {
      *         {@code pool == null || unit == null}
      */
     public SamplingPoolReducer(BasePool pool, long timeInterval, TimeUnit unit, int samples) {
-        forbidIllegalArgument(timeInterval <= 0);
-        forbidIllegalArgument(samples <= 0);
+        forbidIllegalArgument(timeInterval <= 0, String.format("timeInterval %s should be > 0", timeInterval));
+        forbidIllegalArgument(samples <= 0, String.format("samples %s should be > 0", samples));
 
         this.sleepNanoTime = unit.toNanos(timeInterval) / samples;
-        forbidIllegalArgument(sleepNanoTime == 0);
+        forbidIllegalArgument(sleepNanoTime == 0, String.format("sleepNanoTime %s should be > 0", sleepNanoTime));
 
         this.pool = requireNonNull(pool);
         this.samples = samples;