diff --git a/src/logic/pakpage.cpp b/src/logic/pakpage.cpp
index 5e9eab8f..d805a741 100644
--- a/src/logic/pakpage.cpp
+++ b/src/logic/pakpage.cpp
@@ -41,6 +41,7 @@
 // Constructors/Destructors
 //-----------------------------------------------------------------------------
 CPakPageBuilder::CPakPageBuilder()
+	: m_slabCount(0)
 {
 }
 CPakPageBuilder::~CPakPageBuilder()
@@ -66,7 +67,7 @@ PakSlab_s& CPakPageBuilder::FindOrCreateSlab(const int flags, const int align)
 
 	// Try and find a slab that has the same flags, and the closest alignment
 	// of request.
-	for (size_t i = 0; i < m_slabs.size(); i++)
+	for (uint16_t i = 0; i < m_slabCount; i++)
 	{
 		PakSlab_s& slab = m_slabs[i];
 		PakSlabHdr_s& header = slab.header;
@@ -105,10 +106,13 @@ PakSlab_s& CPakPageBuilder::FindOrCreateSlab(const int flags, const int align)
 		return *toReturn;
 	}
 
+	if (m_slabCount + 1 > PAK_MAX_SLAB_COUNT)
+		Error("Out of room while adding new slab; runtime has a limit of %hu.\n", PAK_MAX_SLAB_COUNT);
+
 	// If we didn't have a close match, create a new slab.
-	PakSlab_s& newSlab = m_slabs.emplace_back();
+	PakSlab_s& newSlab = m_slabs[m_slabCount];
 
-	newSlab.index = static_cast<int>(m_slabs.size() - 1);
+	newSlab.index = m_slabCount++;
 	newSlab.header.flags = flags;
 	newSlab.header.alignment = align;
 	newSlab.header.dataSize = 0;
@@ -286,22 +290,28 @@ const PakPageLump_s CPakPageBuilder::CreatePageLump(const int size, const int fl
 //-----------------------------------------------------------------------------
 void CPakPageBuilder::PadSlabsAndPages()
 {
-	int lastPageSizeAligned = 0;
-	int lastPageAlign = 0;
+	struct PageAlignmentTracker_s
+	{
+		int lastPageSizeAligned = 0;
+		int lastPageAlign = 0;
+	};
+
+	PageAlignmentTracker_s alignTrack[PAK_MAX_SLAB_COUNT];
 
 	for (PakPage_s& page : m_pages)
 	{
 		PakPageHdr_s& pageHdr = page.header;
 		PakSlab_s& slab = m_slabs[pageHdr.slabIndex];
 		PakSlabHdr_s& slabHdr = slab.header;
+		PageAlignmentTracker_s& track = alignTrack[pageHdr.slabIndex];
 
 		const int pageSize = pageHdr.dataSize;
 		const int pageAlign = pageHdr.alignment;
 
 		// The runtime pads the previous page to align our current page, we have
 		// to add this extra size to the slab to accommodate for this.
-		if (lastPageSizeAligned > 0 && pageAlign > lastPageAlign)
-			slabHdr.dataSize += IALIGN(lastPageSizeAligned, pageAlign) - lastPageSizeAligned;
+		if (track.lastPageSizeAligned > 0 && pageAlign > track.lastPageAlign)
+			slabHdr.dataSize += IALIGN(track.lastPageSizeAligned, pageAlign) - track.lastPageSizeAligned;
 
 		const int pagePadAmount = IALIGN(pageSize, pageAlign) - pageSize;
 
@@ -312,8 +322,8 @@ void CPakPageBuilder::PadSlabsAndPages()
 		if (pagePadAmount > 0)
 			slabHdr.dataSize += pagePadAmount;
 
-		lastPageSizeAligned = pageSize + pagePadAmount;
-		lastPageAlign = pageAlign;
+		track.lastPageSizeAligned = pageSize + pagePadAmount;
+		track.lastPageAlign = pageAlign;
 	}
 }
 
@@ -322,8 +332,9 @@ void CPakPageBuilder::PadSlabsAndPages()
 //-----------------------------------------------------------------------------
 void CPakPageBuilder::WriteSlabHeaders(BinaryIO& out) const
 {
-	for (const PakSlab_s& slab : m_slabs)
+	for (uint16_t i = 0; i < m_slabCount; i++)
 	{
+		const PakSlab_s& slab = m_slabs[i];
 		out.Write(slab.header);
 	}
 }
diff --git a/src/logic/pakpage.h b/src/logic/pakpage.h
index ca6d61cd..ea1387ee 100644
--- a/src/logic/pakpage.h
+++ b/src/logic/pakpage.h
@@ -1,6 +1,9 @@
 #pragma once
 #include "public/rpak.h"
 
+// Maximum number of slabs that can be allocated into the runtime collection.
+#define PAK_MAX_SLAB_COUNT 20
+
 // Pages can only be merged with other pages with equal flags and an alignment
 // equal or higher than its own if the combined size aligned to the page's
 // new alignment is below this value.
@@ -62,7 +65,7 @@ class CPakPageBuilder
 	CPakPageBuilder();
 	~CPakPageBuilder();
 
-	inline uint16_t GetSlabCount() const { return static_cast<uint16_t>(m_slabs.size()); }
+	inline uint16_t GetSlabCount() const { return m_slabCount; }
 	inline uint16_t GetPageCount() const { return static_cast<uint16_t>(m_pages.size()); }
 
 	const PakPageLump_s CreatePageLump(const int size, const int flags, const int align, void* const buf = nullptr);
@@ -78,6 +81,8 @@ class CPakPageBuilder
 	PakPage_s& FindOrCreatePage(const int flags, const int align, const int size);
 
 private:
-	std::vector<PakSlab_s> m_slabs;
+	std::array<PakSlab_s, PAK_MAX_SLAB_COUNT> m_slabs;
+	uint16_t m_slabCount;
+
 	std::vector<PakPage_s> m_pages;
 };
diff --git a/src/pch.h b/src/pch.h
index 46b274ad..40fd697b 100644
--- a/src/pch.h
+++ b/src/pch.h
@@ -10,6 +10,7 @@
 #include <unordered_set>
 //#include <sysinfoapi.h>
 #include <vector>
+#include <array>
 #include <cstdint>
 #include <string>
 #include <fstream>