diff --git a/examples/aes-cmac/aes-cmac.cpp b/examples/aes-cmac/aes-cmac.cpp
index 194c0037..ff921190 100644
--- a/examples/aes-cmac/aes-cmac.cpp
+++ b/examples/aes-cmac/aes-cmac.cpp
@@ -195,6 +195,11 @@ protected:
 class ClientSideProvider : public QCA::Provider
 {
 public:
+        int version() const
+        {
+                return QCA_VERSION;
+        }
+
         QString name() const
         {
                 return "exampleClientSideProvider";
diff --git a/include/QtCrypto/qca_core.h b/include/QtCrypto/qca_core.h
index 758cadc2..014315d3 100644
--- a/include/QtCrypto/qca_core.h
+++ b/include/QtCrypto/qca_core.h
@@ -46,6 +46,8 @@
 #include "qca_support.h"
 #include "qca_tools.h"
 
+QCA_EXPORT int qcaVersion();
+
 /** 
  * QCA - the Qt Cryptographic Architecture
  */
@@ -605,6 +607,19 @@ namespace QCA
 		 */
 		virtual void init();
 
+		/**
+		 * Target QCA version for the provider.
+		 *
+		 * This is used to verify compatibility between the
+		 * provider and QCA.  For a provider to be used, it
+		 * must have major and minor version numbers that are
+		 * less-than or equal to the QCA version (the patch
+		 * version number is ignored).  This means an older
+		 * provider may be used with a newer QCA, but a newer
+		 * provider cannot be used with an older QCA.
+		 */
+		virtual int version() const = 0;
+
 		/**
 		 * The name of the provider.
 		 * 
diff --git a/plugins/qca-openssl/qca-openssl.cpp b/plugins/qca-openssl/qca-openssl.cpp
index ee5bbe15..3000f4cd 100644
--- a/plugins/qca-openssl/qca-openssl.cpp
+++ b/plugins/qca-openssl/qca-openssl.cpp
@@ -5882,6 +5882,11 @@ public:
 		// todo: any shutdown?
 	}
 
+	int version() const
+	{
+		return QCA_VERSION;
+	}
+
 	QString name() const
 	{
 		return "qca-openssl";
diff --git a/src/qca_core.cpp b/src/qca_core.cpp
index 1b8e7b59..7a5eb351 100644
--- a/src/qca_core.cpp
+++ b/src/qca_core.cpp
@@ -31,6 +31,11 @@
 # include <unistd.h>
 #endif
 
+int qcaVersion()
+{
+	return QCA_VERSION;
+}
+
 namespace QCA {
 
 // from qca_tools
diff --git a/src/qca_default.cpp b/src/qca_default.cpp
index 67133714..8e72121f 100644
--- a/src/qca_default.cpp
+++ b/src/qca_default.cpp
@@ -900,6 +900,11 @@ public:
 		srand(t);
 	}
 
+	int version() const
+	{
+		return QCA_VERSION;
+	}
+
 	QString name() const
 	{
 		return "default";
diff --git a/src/qca_plugin.cpp b/src/qca_plugin.cpp
index 6277eba4..5b5f7e66 100644
--- a/src/qca_plugin.cpp
+++ b/src/qca_plugin.cpp
@@ -34,6 +34,14 @@ static void logDebug(const QString &str)
 		g_pluginman->appendDiagnosticText(str + '\n');
 }
 
+static bool validVersion(int ver)
+{
+	// make sure the provider isn't newer than qca
+	if((ver & 0xffff00) <= (QCA_VERSION & 0xffff00))
+		return true;
+	return false;
+}
+
 class PluginInstance
 {
 private:
@@ -263,6 +271,14 @@ void ProviderManager::scan()
 				continue;
 			}
 
+			int ver = i->p->version();
+			if(!validVersion(ver))
+			{
+				logDebug(QString().sprintf("plugin version 0x%06x is in the future", ver));
+				delete i;
+				continue;
+			}
+
 			addItem(i, -1);
 		}
 		scanned_static = true;
@@ -322,6 +338,14 @@ void ProviderManager::scan()
 				continue;
 			}
 
+			int ver = i->p->version();
+			if(!validVersion(ver))
+			{
+				logDebug(QString().sprintf("plugin version 0x%06x is in the future", ver));
+				delete i;
+				continue;
+			}
+
 			addItem(i, -1);
 		}
 	}
@@ -336,6 +360,13 @@ bool ProviderManager::add(Provider *p, int priority)
 		return false;
 	}
 
+	int ver = p->version();
+	if(!validVersion(ver))
+	{
+		logDebug(QString().sprintf("plugin version 0x%06x is in the future", ver));
+		return false;
+	}
+
 	ProviderItem *i = ProviderItem::fromClass(p);
 	addItem(i, priority);
 	return true;
diff --git a/unittest/clientplugin/clientplugin.cpp b/unittest/clientplugin/clientplugin.cpp
index efca0e7d..b6b63a05 100644
--- a/unittest/clientplugin/clientplugin.cpp
+++ b/unittest/clientplugin/clientplugin.cpp
@@ -54,6 +54,11 @@ void ClientPlugin::cleanupTestCase()
 class TestClientProvider : public QCA::Provider
 {
 public:
+        int version() const
+        {
+                return QCA_VERSION;
+        }
+
         QString name() const
         {
                 return "testClientSideProvider";