diff --git a/src/exchange/taler-exchange-httpd.c b/src/exchange/taler-exchange-httpd.c
index 327bcd1e5..ffd61873b 100644
--- a/src/exchange/taler-exchange-httpd.c
+++ b/src/exchange/taler-exchange-httpd.c
@@ -127,6 +127,11 @@ static unsigned int connection_timeout = 30;
  */
 static int connection_close;
 
+/**
+ * -I command-line flag given?
+ */
+int TEH_check_invariants;
+
 /**
  * True if we should commit suicide once all active
  * connections are finished.
@@ -1903,6 +1908,10 @@ main (int argc,
                                "connection-close",
                                "force HTTP connections to be closed after each request",
                                &connection_close),
+    GNUNET_GETOPT_option_flag ('I',
+                               "check-invariants",
+                               "enable expensive invariant checks",
+                               &TEH_check_invariants),
     GNUNET_GETOPT_option_flag ('r',
                                "allow-reuse-address",
                                "allow multiple HTTPDs to listen to the same port",
diff --git a/src/exchange/taler-exchange-httpd.h b/src/exchange/taler-exchange-httpd.h
index 4f59a5821..9a7395011 100644
--- a/src/exchange/taler-exchange-httpd.h
+++ b/src/exchange/taler-exchange-httpd.h
@@ -144,6 +144,11 @@ extern const struct GNUNET_CONFIGURATION_Handle *TEH_cfg;
  */
 extern char *TEH_exchange_directory;
 
+/**
+ * -I command-line flag given?
+ */
+extern int TEH_check_invariants;
+
 /**
  * Are clients allowed to request /keys for times other than the
  * current time? Allowing this could be abused in a DoS-attack