diff -up qtbase-everywhere-src-5.12.1/src/plugins/sqldrivers/configure.json.firebird qtbase-everywhere-src-5.12.1/src/plugins/sqldrivers/configure.json
--- qtbase-everywhere-src-5.12.1/src/plugins/sqldrivers/configure.json.firebird	2019-01-28 11:11:52.000000000 -0600
+++ qtbase-everywhere-src-5.12.1/src/plugins/sqldrivers/configure.json	2019-02-03 13:41:27.392305128 -0600
@@ -49,10 +49,11 @@
         "ibase": {
             "label": "InterBase",
             "test": {},
-            "headers": "ibase.h",
+            "headers": "ibase.h",
             "sources": [
                 { "libs": "-lgds32_ms", "condition": "config.win32" },
-                { "libs": "-lgds", "condition": "!config.win32" }
+                { "libs": "-lgds", "condition": "!config.win32" },
+                { "libs": "-lfbclient", "condition": "!config.win32" }
             ]
         },
         "mysql": {