diff --git a/src/ints/int10_char.cpp b/src/ints/int10_char.cpp
index 9915b787..415a0589 100644
--- a/src/ints/int10_char.cpp
+++ b/src/ints/int10_char.cpp
@@ -215,7 +215,8 @@ void INT10_ScrollWindow(Bit8u rul,Bit8u cul,Bit8u rlr,Bit8u clr,Bit8s nlines,Bit
 				(real_readb(BIOSMEM_SEG, BIOSMEM_CRTCPU_PAGE) >> 3) & 0x7;
 
 			base = cpupage << 14;
-			base += page*real_readw(BIOSMEM_SEG,BIOSMEM_PAGE_SIZE);
+			if (page!=0xff)
+				base += page*real_readw(BIOSMEM_SEG,BIOSMEM_PAGE_SIZE);
 		}
 	}
 
diff --git a/src/ints/int10_modes.cpp b/src/ints/int10_modes.cpp
index 4c8d4609..e27a4e31 100644
--- a/src/ints/int10_modes.cpp
+++ b/src/ints/int10_modes.cpp
@@ -385,9 +385,18 @@ static void FinishSetMode(bool clearmem) {
 	/* Clear video memory if needs be */
 	if (clearmem) {
 		switch (CurMode->type) {
+		case M_TANDY16:
+			if ((machine==MCH_PCJR) && (CurMode->mode >= 9)) {
+				// PCJR cannot access the full 32k at 0xb800
+				for (Bit16u ct=0;ct<16*1024;ct++) {
+					// 0x1800 is the last 32k block in 128k, as set in the CRTCPU_PAGE register 
+					real_writew(0x1800,ct*2,0x0000);
+				}
+				break;
+			}
+			// fall-through
 		case M_CGA4:
 		case M_CGA2:
-		case M_TANDY16:
 			for (Bit16u ct=0;ct<16*1024;ct++) {
 				real_writew( 0xb800,ct*2,0x0000);
 			}