diff --git a/src/PGConnection+Private.h b/src/PGConnection+Private.h
new file mode 100644
index 0000000..5c64703
--- /dev/null
+++ b/src/PGConnection+Private.h
@@ -0,0 +1,9 @@
+#import "PGConnection.h"
+
+OF_ASSUME_NONNULL_BEGIN
+
+@interface PGConnection ()
+- (PGconn *)PG_connection;
+@end
+
+OF_ASSUME_NONNULL_END
diff --git a/src/PGConnection.h b/src/PGConnection.h
index 365a95a..81ae498 100644
--- a/src/PGConnection.h
+++ b/src/PGConnection.h
@@ -8,7 +8,7 @@ OF_ASSUME_NONNULL_BEGIN
 
 @interface PGConnection: OFObject
 {
-	PGconn *_connnection;
+	PGconn *_connection;
 	OFDictionary OF_GENERIC(OFString *, OFString *) *_parameters;
 }
 
@@ -18,10 +18,9 @@ OF_ASSUME_NONNULL_BEGIN
 - (void)connect;
 - (void)reset;
 - (void)close;
-- (PGResult *)executeCommand: (OFConstantString *)command;
-- (PGResult *)executeCommand: (OFConstantString *)command
+- (nullable PGResult *)executeCommand: (OFConstantString *)command;
+- (nullable PGResult *)executeCommand: (OFConstantString *)command
 		  parameters: (id)firstParameter, ... OF_SENTINEL;
-- (PGconn *)PG_connection;
 - (void)insertRow: (OFDictionary *)row
 	intoTable: (OFString *)table;
 - (void)insertRows: (OFArray OF_GENERIC(OFDictionary *) *)rows
diff --git a/src/PGConnection.m b/src/PGConnection.m
index 88a4cb2..17b2b5e 100644
--- a/src/PGConnection.m
+++ b/src/PGConnection.m
@@ -1,4 +1,7 @@
 #import "PGConnection.h"
+#import "PGConnection+Private.h"
+#import "PGResult.h"
+#import "PGResult+Private.h"
 
 #import "PGConnectionFailedException.h"
 #import "PGCommandFailedException.h"
@@ -34,10 +37,10 @@
 			    @"%@=%@", key, object];
 	}
 
-	if ((_connnection = PQconnectdb([connectionInfo UTF8String])) == NULL)
+	if ((_connection = PQconnectdb([connectionInfo UTF8String])) == NULL)
 		@throw [OFOutOfMemoryException exception];
 
-	if (PQstatus(_connnection) == CONNECTION_BAD)
+	if (PQstatus(_connection) == CONNECTION_BAD)
 		@throw [PGConnectionFailedException
 		    exceptionWithConnection: self];
 
@@ -46,20 +49,20 @@
 
 - (void)reset
 {
-	PQreset(_connnection);
+	PQreset(_connection);
 }
 
 - (void)close
 {
-	if (_connnection != NULL)
-		PQfinish(_connnection);
+	if (_connection != NULL)
+		PQfinish(_connection);
 
-	_connnection = NULL;
+	_connection = NULL;
 }
 
 - (PGResult *)executeCommand: (OFConstantString *)command
 {
-	PGresult *result = PQexec(_connnection, [command UTF8String]);
+	PGresult *result = PQexec(_connection, [command UTF8String]);
 
 	if (PQresultStatus(result) == PGRES_FATAL_ERROR) {
 		PQclear(result);
@@ -126,7 +129,7 @@
 				    UTF8String];
 		} while ((parameter = va_arg(args, id)) != nil);
 
-		result = PQexecParams(_connnection, [command UTF8String],
+		result = PQexecParams(_connection, [command UTF8String],
 		    argsCount, NULL, values, NULL, NULL, 0);
 	} @finally {
 		[self freeMemory: values];
@@ -194,7 +197,7 @@
 
 		[command appendString: @")"];
 
-		result = PQexecParams(_connnection, [command UTF8String],
+		result = PQexecParams(_connection, [command UTF8String],
 		    (int)count, NULL, values, NULL, NULL, 0);
 	} @finally {
 		[self freeMemory: values];
@@ -222,6 +225,6 @@
 
 - (PGconn *)PG_connection
 {
-	return _connnection;
+	return _connection;
 }
 @end
diff --git a/src/PGResult+Private.h b/src/PGResult+Private.h
new file mode 100644
index 0000000..bf08c17
--- /dev/null
+++ b/src/PGResult+Private.h
@@ -0,0 +1,11 @@
+#import "PGResult.h"
+
+OF_ASSUME_NONNULL_BEGIN
+
+@interface PGResult ()
++ (instancetype)PG_resultWithResult: (PGresult *)result;
+- PG_initWithResult: (PGresult *)result OF_METHOD_FAMILY(init);
+- (PGresult *)PG_result;
+@end
+
+OF_ASSUME_NONNULL_END
diff --git a/src/PGResult.h b/src/PGResult.h
index 354c817..c2a71f8 100644
--- a/src/PGResult.h
+++ b/src/PGResult.h
@@ -10,10 +10,6 @@ OF_ASSUME_NONNULL_BEGIN
 {
 	PGresult *_result;
 }
-
-+ (instancetype)PG_resultWithResult: (PGresult *)result;
-- PG_initWithResult: (PGresult *)result OF_METHOD_FAMILY(init);
-- (PGresult *)PG_result;
 @end
 
 OF_ASSUME_NONNULL_END
diff --git a/src/PGResult.m b/src/PGResult.m
index b6ca303..daeea81 100644
--- a/src/PGResult.m
+++ b/src/PGResult.m
@@ -1,13 +1,14 @@
 #import "PGResult.h"
 #import "PGResultRow.h"
+#import "PGResultRow+Private.h"
 
 @implementation PGResult
-+ PG_resultWithResult: (PGresult *)result
++ (instancetype)PG_resultWithResult: (PGresult *)result
 {
 	return [[[self alloc] PG_initWithResult: result] autorelease];
 }
 
-- PG_initWithResult: (PGresult *)result
+- (instancetype)PG_initWithResult: (PGresult *)result
 {
 	self = [super init];
 
@@ -34,8 +35,8 @@
 	if (index > PQntuples(_result))
 		@throw [OFOutOfRangeException exception];
 
-	return [PGResultRow rowWithResult: self
-				      row: (int)index];
+	return [PGResultRow PG_rowWithResult: self
+					 row: (int)index];
 }
 
 - (PGresult *)PG_result
diff --git a/src/PGResultRow+Private.h b/src/PGResultRow+Private.h
new file mode 100644
index 0000000..31b8eb6
--- /dev/null
+++ b/src/PGResultRow+Private.h
@@ -0,0 +1,12 @@
+#import "PGResultRow.h"
+
+OF_ASSUME_NONNULL_BEGIN
+
+@interface PGResultRow ()
++ (instancetype)PG_rowWithResult: (PGResult *)result
+			     row: (int)row;
+- PG_initWithResult: (PGResult *)result
+		row: (int)row OF_METHOD_FAMILY(init);
+@end
+
+OF_ASSUME_NONNULL_END
diff --git a/src/PGResultRow.h b/src/PGResultRow.h
index f1c1432..be481fa 100644
--- a/src/PGResultRow.h
+++ b/src/PGResultRow.h
@@ -6,17 +6,12 @@
 
 OF_ASSUME_NONNULL_BEGIN
 
-@interface PGResultRow: OFDictionary
+@interface PGResultRow: OFDictionary OF_GENERIC(OFString *, id)
 {
 	PGResult *_result;
 	PGresult *_res;
 	int _row;
 }
-
-+ rowWithResult: (PGResult *)result
-	    row: (int)row;
-- initWithResult: (PGResult *)result
-	     row: (int)row;
 @end
 
 OF_ASSUME_NONNULL_END
diff --git a/src/PGResultRow.m b/src/PGResultRow.m
index f6d7f9d..3920539 100644
--- a/src/PGResultRow.m
+++ b/src/PGResultRow.m
@@ -1,4 +1,5 @@
 #import "PGResultRow.h"
+#import "PGResult+Private.h"
 
 static id
 convertType(PGresult *res, int column, OFString *string)
@@ -45,8 +46,8 @@ convertType(PGresult *res, int column, OFString *string)
 @end
 
 @implementation PGResultRow
-+ rowWithResult: (PGResult *)result
-	    row: (int)row
++ (instancetype)rowWithResult: (PGResult *)result
+			  row: (int)row
 {
 	return [[[self alloc] initWithResult: result
 					 row: row] autorelease];
diff --git a/src/exceptions/PGException.m b/src/exceptions/PGException.m
index c451872..0f8a468 100644
--- a/src/exceptions/PGException.m
+++ b/src/exceptions/PGException.m
@@ -1,4 +1,5 @@
 #import "PGException.h"
+#import "PGConnection+Private.h"
 
 @implementation PGException
 @synthesize connection = _connection;