diff --git a/libgnucash/engine/gncAddressP.h b/libgnucash/engine/gncAddressP.h
index f3c1d856e3..b2e5aca3b9 100644
--- a/libgnucash/engine/gncAddressP.h
+++ b/libgnucash/engine/gncAddressP.h
@@ -30,6 +30,14 @@
 
 #include "gncAddress.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 gboolean gncAddressRegister (void);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* GNC_ADDRESSP_H_ */
diff --git a/libgnucash/engine/gncCustomerP.h b/libgnucash/engine/gncCustomerP.h
index 7a12387d1a..4804cf06ba 100644
--- a/libgnucash/engine/gncCustomerP.h
+++ b/libgnucash/engine/gncCustomerP.h
@@ -31,6 +31,10 @@
 
 #include "gncCustomer.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 gboolean gncCustomerRegister (void);
 gchar *gncCustomerNextID (QofBook *book);
 const gnc_numeric *gncCustomerGetCachedBalance (GncCustomer *cust);
@@ -38,4 +42,8 @@ void gncCustomerSetCachedBalance (GncCustomer *cust, const gnc_numeric *new_bal)
 
 #define gncCustomerSetGUID(E,G) qof_instance_set_guid(QOF_INSTANCE(E),(G))
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* GNC_CUSTOMERP_H_ */
diff --git a/libgnucash/engine/gncEmployeeP.h b/libgnucash/engine/gncEmployeeP.h
index 8dd6e47ac3..5d8abb2140 100644
--- a/libgnucash/engine/gncEmployeeP.h
+++ b/libgnucash/engine/gncEmployeeP.h
@@ -31,6 +31,10 @@
 
 #include "gncEmployee.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 gboolean gncEmployeeRegister (void);
 gchar *gncEmployeeNextID (QofBook *book);
 const gnc_numeric *gncEmployeeGetCachedBalance (GncEmployee *vend);
@@ -38,4 +42,8 @@ void gncEmployeeSetCachedBalance (GncEmployee *vend, const gnc_numeric *new_bal)
 
 #define gncEmployeeSetGUID(E,G) qof_instance_set_guid(QOF_INSTANCE(E),(G))
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* GNC_EMPLOYEEP_H_ */
diff --git a/libgnucash/engine/gncJobP.h b/libgnucash/engine/gncJobP.h
index f3b2ddebd4..a04ae3a14f 100644
--- a/libgnucash/engine/gncJobP.h
+++ b/libgnucash/engine/gncJobP.h
@@ -31,9 +31,17 @@
 
 #include "gncJob.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 gboolean gncJobRegister (void);
 gchar *gncJobNextID (QofBook *book);
 
 #define gncJobSetGUID(E,G) qof_instance_set_guid(QOF_INSTANCE(E),(G))
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* GNC_JOBP_H_ */
diff --git a/libgnucash/engine/gncOrderP.h b/libgnucash/engine/gncOrderP.h
index c7e5f302cd..baad43ccd8 100644
--- a/libgnucash/engine/gncOrderP.h
+++ b/libgnucash/engine/gncOrderP.h
@@ -31,9 +31,17 @@
 
 #include "gncOrder.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 gboolean gncOrderRegister (void);
 gchar *gncOrderNextID (QofBook *book);
 
 #define gncOrderSetGUID(O,G) qof_instance_set_guid(QOF_INSTANCE(O),(G))
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* GNC_ORDERP_H_ */
diff --git a/libgnucash/engine/gncVendorP.h b/libgnucash/engine/gncVendorP.h
index 66c183d14e..175ec6f58d 100644
--- a/libgnucash/engine/gncVendorP.h
+++ b/libgnucash/engine/gncVendorP.h
@@ -30,6 +30,10 @@
 
 #include "gncVendor.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 gboolean gncVendorRegister (void);
 gchar *gncVendorNextID (QofBook *book);
 const gnc_numeric *gncVendorGetCachedBalance (GncVendor *vend);
@@ -38,4 +42,8 @@ void gncVendorSetCachedBalance (GncVendor *vend, const gnc_numeric *new_bal);
 #define gncVendorSetGUID(V,G) qof_instance_set_guid(QOF_INSTANCE(V),(G))
 
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* GNC_VENDORP_H_ */